Re ta tee NE Rf ttn Minas Nectar te Stet LARPS ie Naso yp chsson dng eOy hatha Incite Ree nar a a neice irene ecg een aoe an a 2 Fim Sg Rigel tal whe Pra hs Nomam. Pinte apie hail Rats tama iearartieaet ABest E THE GEOLOGICAL MAGAZINE. DECADE VI. VOL. III. JANUARY—DECEMBER, 1916. NH THE SEROLOGICAL MAGAZINE Monthly Jounal of Geologn. aah Gab, © LO G LS ik. NOS. DCXIX TO DCXXX. EDITED BY HENRY WOODWARD, LL.D., F.R.S., F.G.8., V.P.Z.8., F.R.M.S. LATE OF THE BRITISH MUSEUM OF NATURAL HISTORY; PRESIDENT OF THE PALHONTOGRAPHICAL SOCIETY ;. ETC. ASSISTED BY Prorrssor J. W. GREGORY, D.Sc., F.R.S., F.G.S. Dr. GEORGE J. HINDE, F.RBS., F.G.S. Sm T. H. HOLLAND, K.C.LE., A.R.C.S., D.Sc., F.R.S., V.P.G.S. JOHN EDWARD MARR, M.A., Sc.D. (Camb.), F.R.S., F.G.S. Sm JETHRO TEALL, M.A., Sc.D. (Camb.), LL.D., F.RB.S., F.G.S. Prornsson W. W. WATTS, Sc.D., LL.D., M.Sc., F.R.S., F.G.S. De. ARTHUR SMITH WOODWARD, LL.D., F.RB.S., F.LS., V.P.G.S. NEW SHRIBS. DHCADE VI- VOL. II. -JANUARY—DECEMBER, 1916. 4 ZZSOUR LONDON: DULAU & CO., LTD., 37 SOHO SQUARE, W. 1916. STEPHEN AUSTIN AND SONS, LTD. PRINTERS, HERTFORD. ise Oh AAS: FACING PAGE . Restored Skeleton of Stenomylus hitchcocki, Loomis Saurostomus esocinus, Agassiz; Upper Lias, Holzmaden . Terebratulid Shell-structures Map of the Fluvio-glacial Gravels, Thames Valley . Portrait of Arthur Vaughan, B.A., D.Sc. Chalk Polyzoa Two Obsidianites, Singapore Lower Lias Ammonite, Dorset . Tridymite and Quartz, Iceland Chalk Polyzoa Portrait of Dr. John E. Marr, F.R.S. Some Wealden Sands Pit and Mound Structures developed during Sedimentation Chalk Polyzoa New Extinct Bird, South Carolina . Voleanie Rocks, Iceland . Triassic Fossils, Leicestershire Chalk Polyzoa New Guinea Corals . 1 ol fay h te LIST OF ILLUSTRATIONS IN THE TEXT. PAGE Trail and Underplight . : : ; : : : ‘ : : 3 Wax and pitch =. d : : ; : : : ; : : 5 Sketch-map of Permian formation in Maritime Alps . : : > 10 Sections of Permian formation, Maritime Alps . : : ; Beane ab Map of West Cumberland . ; F : Q : : i 5 IS Diagrams showing amount of water and sulphuric acid in St. Bees Sandstone : ; ‘ : : : F ; : : A vcs HS) ' Diagrams showing variation in number of puncte of Terebratula punctata and T. biplicata : ; 5 3 : : - 55 Sections of overflow channels, Murk Mire Moor . 6 : : aE: Plan of adoral surface of Lovenia forbesi . : : 3 : . 102 Second figure for comparison : : 3 i F : : . 103 Ball and pillow-form structures in rocks : ; : 3 : . 147 Shell-jointing in sandstone . : : ‘ 5 ; : : . 148 Ball structures in sandstone . : : 5 : : : : . 149 Sandstone ‘ball’, Tyddyn-main . A ; 3 : ‘ : . 149 Contorted layers in sandstone 3 ‘ F : : : 4 . 150 ' Diagram showing curved cleavage : 5 : 3 : : . 153 Folded layers of sandstone and shale . : : : é F . 153 Sandstone in shale ‘ ; : ; ; ; ‘ : : . 154 Map of crystalline rock-areas, Piédmont : : : : : . 199 Drawing of aggregate of Pl. IX, Fig.5. : : : : : . 207 Drawing of a single quartz individual . : : : . } . 208 Map of South Wales Coal-field . : : : : : ‘ ee Locality map of New Zealand . : : ; é : 2 . 244 Sections of Monte Viso and Rocciamelone . : i : : . 251 Mandible of Nautilus pompilius . ? ; : : 4 : . 261 Mandible of Nawtilus (Rhyncholithes butleri, n.sp.) sp. . : 5 GR Diagram of distribution of temperature in depth . : : : . 269 Sketch-map of crystalline rock-areas, Northern Piémont : : . 3806 Stripped fossil denudation plain . : : : : : : _ BG Zocecia of three Bryozoa from Norseman Limestone . : ‘ 3 BRL Trogonthertum from Copford : ; 5 ; : : ; a BB Section of brick-pit, Barnwell Station . : ; : : ; . 841 Sketch-plan of Lanzo Valleys, Grajan Alps. : : 5 : . 3849 vill List of Illustrations in the Text. Section of liparite exposure . : : 5 : Section showing outcrop of the Coral Rag and Ampthill Clay Sketch-map of crystalline massif, Savona Sections of crystalline massif, Savona . The Kegworth footprint Map of Voltri Group, Western Liguria Map and sections of ophiolithic groups, Eastern Liguria Map of ophiolithic groups, Hastern Liguria . Dallina floridana, Pourtales Section of coral, New Guinea Small glacier, showing the snow-line Diagram of earth’s areas mapped in 1860 and 1916 cA PAGE 392 402 403 422 - 448 491 492 501 530 538 568 a Price 2s. net. 3 lonthts Journal of Geology. WITH WHICH IS INCORPORATED THE GHOLOGIST. EDITED BY HENRY WOODWARD, LL.D., &c. F.R.S., F.G.S., ASSISTED BY PROFESSOR J. W. GREGORY, D.Sc., F.R.S., F.G.S. DR. GEORGE J. HINDE, F.R.S., F.G.S. Sir THOMAS H, HOLLAND, K.C.IE., A.R.C.S., D.Sc., F.R.S., F.G.S. . JOHN EDWARD MARR, M.A.,, Se.D. (Cams.), F.R.S., F.G.S. . J. J. H. 'FHALG, M.A., Sc.D. (Cams.),-LU.D., F.R.S., F.G.S. PROFESSOR W. W. WATTS, Sc.D., M.Sc., F.R.S., VICE-PRES. GEOL, Soc. DR. ARTHUR SMITH WOODWARD, F.RB.S., ES PRES. GEOL, Soc. JANUARY, 1916. “AN 24 joie } - = Con THN Tse I. ORIGINAL ARTICLES. Page . IIL. Reviews. Page an a Mounted Skeleton of a Dr. A. Keith’s Antiquity of Man... 32 ae ‘Gazelle-Camel’. By ©. W. Prehistoric Archeology... ... ... B4= ANDREWS, D.Sc.,F.R.S. (Pl. 1.) 1 | Pleistocene Mammals, Iowa... 35 - Trail and Underplight. By R. M. Coal-measure Amphibia 35 DEELEY, M-inst.C.E., F.G.S. New York State Museum 36 AWith 2iVext-fioures:)< 7. 41. 2 The Trilobite Harpes 36 _ Axinite Veins in Penmaenmawr The Edrioasteroidea 37 poor. ie OC. SARGENT, H. A. Allen : Cretaceous Mollusca 37 z F.G.S. 5 | Professor J. Barrell: Isostasy, etc. 38 : ee Hoeniation:. in tae Alps of. Delta Deposits of Nile aes ee Piémont, Dauphiné, and Savoy. Doelter’s Mineralogy 39 By C. 8. Du RICHE PRELLER, A Russian Meteorite 40 M.A., Ph.D., F.G.S., F.BR.S.E. Brief Notices : Mineral Production ie (With 2 Page-illustrations.) ... 7 of India—Porosity of Rocks, Sw gts St. Bees Sandstone of West Karroo—Brighton’s Lost River.. 40 Cumberland. By StipNEY MEL- IV. REPORTS AND PROCEEDINGS, -. MORE. (With 2 Text-figures.)... 17 | Geological Society of Glasgow Al Brachiopod Morphology. By J. Geological Society of London— - WILFRID JACKSON, F.G.S. ... 21 November 17, 1915 : 42 - Glacier Lake Channels. By Pyro- December 1 . : Ad fessor PERCY Fry KENDALL 26 | Mineralogical Society 44 ees : V. CORRESPONDENCE. It. Novices oF Memoirs. Bernard Smith, M.A. ... .. 45 _ Ordovician, Cader Idris. By A. H. Professor T. G. Bonney, M.A., D.Sc. 47- - Cox and A. K. Wells... 30 | Dr. M. C. Stopes oe 47 Corrosive Brines, Manitoba. By VI. OBITUARY. Professor ‘R. C. Wallace, M.A 31 | Dr. Arthur Vaughan, M.A. 48 LONDON: DULAU & CO., a 387 SOHO SQUARE, W. ude, ee my Born = 247 a Dich elle, Eonar ea a ar Fic. 1.—Sketch-plan. Scale 1 : 1,000,000. M= Miocene. P= Permian. Ho= Hocene. C= Carboniferous. L=Lias. CS =Cale-schist ) Nea IMI Naais, G=Gneiss J Fic. 2.—Section of Montgioie (2,631 m.), S. to N. Scale 1: 1,000,000. T, 1, m, u= Lower, Middle, and Upper Trias. : “i Zi \ Enel WIRED nee aa if Anyemenge RSS LZ; ii Ay} Wi Mid Fic. 3.—Section of Cime de Rochettee (2,476 m.), S. to N. x = porphyritic mass. D. R, P. del. 12 _ Dr. Dw Riche Preller—Permian in The Permian formation reaches a thickness of at least 1,000 metres, and rests directly and conformably upon the fossiliferous Carboniferous strata, which attain about half that visible depth and constitute the lowest zone of the Montgioie range. The latter strata are, as usual in the Alps, composed in the main of blackish carbonaceous and grey micaceous schists, graduating into talcose greenish cale- schists, which become felspathic and then pass into quartzose schist, which forms the base of the Permian formation. The Carboniferous age of the strata underlying the Permian, and consequently the Permian age of the besimaudite zone itself, was definitely established by fossils found in the Negrone Valley near Viozéne, on the southern flank of Montgioie, by Zaccagna, and determined by Professor Portis of Pisa. Soon afterwards this discovery was confirmed independently by Squinabol and by Mazzuoli, both of whom found indubitably Upper Carboniferous fossils in the Bormida valleys already mentioned, where the Carboniferous strata are, moreover, anthracitic.! The distinguishing feature of the besimaudite zone, like that of the equivalent schists of the Apuan Alps, is its gneissiform character, but it also comprises, in upward progression, a variety of associated rocks. Thus, from a granular quartzose schist it passes into greenish- grey compact rock of porphyritic texture with large elongated felspar crystals up to 2 centimetres in length. Again it passes into nodulous gneissiform schist without felspar, or again into sericitic schist, and in places also assumes a granitoid structure, notably above Savona. There are also hornblende-bearing intercalations, simulating the aspect of pietra verde. In Monte Rocchetta occurs a large mass of reddish porphyritic quartzose rock with white mica crystals, which Zaccagna regards as intrusive porphyry, and which also occurs in Monte Abisso, close to the Col di Tenda Pass; but I am disposed to regard both these masses, which, moreover, lie in a zone, rather as Upper Permian, very similar to the red verrucano or sernifite of the Glarus Alps, a clastic rock which often has all the appearance of porphyry. _ The besimaudite zone is directly and conformably overlain by, and graduates into, a coarse conglomerate with white and reddish pebbles in a greenish, taleose matrix. This conglomerate or ‘anagenite’ is of considerable depth in the Montgioie range, and also occurs sparsely in the same position in the Apuan Alps. It represents the Upper Permian or Verrucano formation, and marks a transition from the latter to the Lower Trias. In my opinion, the porphyritic masses of Monte Rocchetta and Abisso already mentioned form part of it. It graduates, in its turn, into the conformably overlying Triassic series of quartzite, grey subcrystalline limestone, and calcareous schists, and these are overlain by banks of blackish, brecciform, marmiferous limestone with white calcite crystals, which is quarried near Villanova, at the northern base of the range, and is conspicuous in A. Portis, Boll. R. Com. Geol., vol. xviii, p. 417, 1887 ; L. Mazzuoli, ibid., p. 6; S. Squinabol, Giornale Scient. Genova, Fascic. Giugno, 1887. The survey of the Ligurian Alps eastward from the Montgioie range, surveyed by Zaccagna, was carried out concordantly by Mazzuoli and Issel, Boll. R. Com. Geol. 1884 et seq. the Alps of Piémont and Savoy. 13 the columns and ornamental architecture of the churches and palaces of Turin. The Triassic series, about 400 metres in thickness, crowns Montgioie and most of the other principal mountains of the range, on the southern base of which occur also some Juraliassic and Cretaceous outcrops, followed by a large area of Kocene lime- and sandstone, while on the north it is bordered by an equally extensive area of Miocene marl and molasse. Thus the stratigraphical sequence of the range, illustrated in the two typical parallel cross-sections of Montgioie and Rocchetta (p. 11, Figs. 2 and 3), exhibits a close analogy to that of the Apuan Alps from thé Permian formation upwards. In the Montgioie range the flexures are inclined to the west, where the strata abut unconformably against the gneiss and granite massif of Mercantour ; in both the Montgioie and the Apuan range there is considerable folding, but no faulting or unconformity, and their uniformity of age, sequence, and general lithological character is abundantly demonstrated. IIT. Tar Permian in tae WEsTERN ALps. From the Montgioie range the Permian formation extends in a westerly direction to the Cottian Alps, and thence continues N. and N.N.E. to the Grajan Alps and the base of Mont Blanc. As the limits of this paper do not admit of a detailed description of the different localities, suffice it to indicate briefly the alignment of this extension of the Permian zone. 1. In Dauphiné. From near Boves at the north-western extremity of the Montgioie range, the Permian, skirting the Monte Viso massif on the right and that of Mercantour on the left, crosses the Stura Valley, and from here forms an uninterrupted zone about 60 kilometres in length and 2 to 5 kilometres wide to the Ubbaye Valley and Mont Chambeyron (38,3888 metres altitude) on the Italo-French frontier. Thence it reappears further north on the south-eastern side of Briancon, near Mont Genévre, and, skirting the frontier, continues for about 15 kilometres to Mont Chaberton (3,135 metres), this zone being about 2 kilometres in width.’ ~ 2. In Savoy. The next outcrop occurs about 20 kilometres north of the last point, near Modane, below the northern end of the Mont Cenis tunnel, in the Are Valley, at an altitude of about 1,000 metres, whence it extends in a belt 5 kilometres in average width to St. Bon, Bozel, and Champagny in the Doron Valley east of Moutiers.* 1 The Mont Genévre group and Mont Chaberton have been dealt with at length in the interesting papers respectively by Cole and Gregory, Q.J.G.S., 1890, p. 305 et seq., and by Davies & Gregory, ibid. 1894, p. 307 et seq. 2 Near Moutiers are the two geologically famous localities of Petit Coeur and Mont Jovet in the Tarantaise district of the Isére Valley. Near Petit Coeur, about 6 kilometres north of Moutiers, the long-debated phenomenon of a Carboniferous, fossiliferous stratum being wedged between two strata of Jurassic fossiliferous limestone was interpreted, among others by Lory, as due to a fault, whereas Zaccagna explained the Carboniferous strip more naturally as the remnant or denuded extremity of a synclinal fold, the other end of which appears in a somewhat larger outcrop at Hautecour, some 6 kilometres east of Moutiers. In Mont Jovet (2,303 metres), on the other hand, the puzzling feature was its being capped by a considerable mass of cale-schist with pietra 14 Dr. Du Riche Preller—Permian in It then reappears— 3. In Northern Piémont above Courmayeur, at the foot of Mont Blane, in the two well-known mountains Chétif and La Saxe (2,343 and 2,358 metres), separated by the Dora Baltea, and again, some 5 kilometres lower down the Dora Valley, in the Pian d’Arp, an eminence near Pré St. Didier. Throughout this more or less continuous belt from the Maritime Alps to Mont Blane the Permian exhibits the besimaudite and verrucano characteristics already described, and runs parallel with, and in normal sequence between, the Carboniferous and the Triassic series, so much so that the three zones, with the addition of a narrow Jurassic zone, all bifurcating at Col de Bonhomme, the south-western spur of Mount Bianc, form a belt, more or less interrupted by denudation, round that massif. Of the Permian outcrops, those of Modane and Courmayeur are of special interest: (1) that of Modane, because Lory and other French geologists included it in their great zone of crystalline metamorphosed ‘Triassic schists, whereas its interposition between Carboniferous and Triassic—both fossiliferous—strata clearly proves its Permian age; and (2) that of Courmayeur, because Chétif and La Saxe were regarded as granitic spurs of the Mont Blanc massif,’ whereas Zaccagna recognized them as the northern extremity of a Permian synclinal fold, which is conformably overlain by the Triassic series, and whose southern extremity is the outcrop of Pian d’Arp near St. Didier, already mentioned. It appears again in the St. Mary Mountain near Aosta, some 20 kilometres down the Dora Valley. In Savoy the Permian zone from the Arc Valley at Modane to the Doron Valley south-east of Moutiers has more recently been considerably enlarged by Termier, more especially in the Vanoise region and in the Doron Valley itself.2 In Dauphiné the crystalline schists of Mont Genévre near Briancon have also been assigned to the Permian, whereas this formation only skirts the western base of that group, and is overlain by dark, indubitably Triassic limestone corresponding to the grezzoni of the Apuan Alps, while the crystalline schists with their diabasic and serpentinous (pietra verde) intercalations are clearly Archeean.? verde or vert des Alpes intercalations, surrounded by a Triassic belt. The former outcrop was regarded by Bertrand as Liassic, while Professor Lory included it in his Triassic metamorphosed schistes lustrés, and lastly, Zaccagna recognized it as schistes lustrés but of Archean age, the pietra verde intercala- tions being conclusive evidence by analogy with Mont Genévre, Susa, etc. Professor Gregory, in his searching analysis of all the evidence (Q.J.G.S., 1896, pp. 1-16), concludes in favour of the pre-Carboniferous age of the Mont Jovet schists, viz. in the absence of the Lower Paleozoic, virtually in favour of their Archean age. 1 The Val Veni depression between these two mountains and the granite massif of Mont Blane is filled with Liassic limestone resting conformably against,the Permian of the former but unconformably against the latter. 2 ‘* Btude sur la constitution géologique du massif de la Vanoise’’: Bull. ‘Carte géol. France, vol. ii, No. 20, 1891. 3 A sketch-section of part of the Mont Genévre group is given in Professor Bonney’s paper, ‘‘ Two Traverses of the Crystalline Rocks of the Alps’: Q.J.G.S., 1889, p. 80. The limestone at the western end is marked Jurassic, probably on the strength of Lory’s map as Lias compacte or calcawe Brianconnais. It is now included in the Trias. the Alps of Prémont and Savoy. 15 TV. Tur PERMIAN IN RELATION TO ARCH#AN AND Mesozoic Scuists. Intimately connected with the stratigraphical position of the Permian is the demarcation of the Archzan and Mesozoic schists. As is well known, both Elie de Beaumont in the French map (1860) and Sismonda in the Italian map (1862) of the Western Alps divided the crystalline rocks into two great zones—a lower one, comprising indiscriminately the Archean gneiss, and the Paleeozoic and Mesozoic series, as the ‘‘ metamorphosed Jurassic area’”’; and an upper one, embracing the Archean granite and all the pietra verde rocks, as intrusive and post-Jurassic. The later maps of Lory and Favre of the French, and of Gastaldi of the Italian side, to some extent disentangled that strange confusion: Lory and Favre by assigning the gneiss, granite, and the ‘‘ vert des Alpes” to the Archean and all the mica- and cale-schists indiscriminately to the Trias as “ schistes lustrés’’, while Gastaldi separated all the pietra verde rocks into. a zone per se as overlying the primitive gneiss and granite zone, and labelled it and the mica- and cale-schists as crystalline rocks, more recent, but pre-Paleozoic. The Permian did not figure in any of those maps. Such was the position in the ’eighties when Zaccagna’s revisionary survey showed those more or less arbitrary classifications to be obsolete and untenable. Accordingly he defined the Archzean as composed of two zones—a lower, comprising exclusively the primitive gneiss and granite rocks, and an upper, embracing the mica-schists (schistes lustrés) and the small-grained tabular gneiss; the calc-schists and erystalline limestone; and the great masses of pietra verde as a con- temporaneous part.! From the Carboniferous formation, till then held - to be the only representative of the Paleozoic in the Maritime and Western Alps, he separated the Permian besimaudite and verrucano zone directly overlain by the indubitably Triassic series in which he included Lory’s ‘‘Lias compacte”’ or Brianconnais limestone. This clear definition of the Lower and Upper Archean, the Upper Paleozoic, and the Lower Mesozoic formations harmonized the two sides of the Western Alps, and was embodied in the new geological map of Italy of 1896, a preliminary sketch of the earlier results in the Maritime and Cottian Alps having been already exhibited at the Berlin Geological Congress of 1885. These were largely, if with variations, adopted by Vasseur and Carez in their geological map of France of the same year.’ Zaccagna’s conclusions were thus, in the main, signally vindicated. 1 The small-grained tabular gneiss (gneiss minuto tabulare) is extensively quarried in the Susa, Chisone, and Pellice Valleys for building purposes in Turin. 2 Vasseur and Carez assign the crystalline schists west of Monte Viso on the Italian side to the Paleozoic (Cambrian), for which, however, there is no warrant, the absence of the Lower Paleozoic in the Western Alps being, on the contrary, an important feature as marking a long interval of erosion which led up to the Carboniferous formation, composed of the sedimentary and calcareous products of that erosion in which were engulfed the vast débris-accumulations of a luxuriant vegetation. The Archran age of the crystalline schists was, after Zaccagna’s publication in 1885, affirmed also by Professor Bonney (1886 and 1889), in relation to the Alps generally. 16 Dr. Du Riche Preller—Permian in the. Alps. In so far as the degree of crystallinity, being the effect of metamorphism under pressure and high temperature, is a test of age, the Archean highly crystalline schists differ from the gneissiform Permian schists as much as do the latter from the still less crystalline Triassic schists, e.g. those of the Apuan Alps as part of the marmiferous zone, albeit both those younger schists often simulate a gneissose aspect. As regards the Archean schists, the presence of igneous rocks, whether primary or altered, is, of course, no absolute criterion of age, but in Piémont the enormous pietra verde masses of Monte Viso, of the Dora Riparia Valley, and of Val d’ Aosta are by alternation, eraduation, and lenticular intercalations, or again as irregular, obviously eruptive deposits, so closely associated with the mica- and cale-schists that their inclusion in the Upper Archean zone appears perfectly legitimate. As in the younger schist-formations, so also in that Archean zone the mica-schists always form the lower part of the zone, gradually passing into calc-schists which predominate in the upper part, with intercalations of saccharoidal limestone, quarried e.g. in the Susa Valley. It is with the upper parts of the mica- and the lower parts of the calc-schists that the pietra verde masses are more especially associated, and the intermediate position of the latter therefore points to their original subaqueous or superficial eruption in the corresponding period.' VY. Conctustion. In the necessarily small sketch-plan (p. 11, Fig. 1) I have traced the Permian zone from the Ligurian Alps near Savona through Southern Piémont, Dauphiné, and Savoy to Mont Blanc, a distance of 250 kilometres. It is seen that the curved alignment of that zone, which would equally apply to the concomitant Carboniferous and Triassic zones, runs, in the main, between and parallel to the two great primitive gneiss and granite belts indicated by dotted lines, the outer belt comprising the Mont Blanc massif and the Pelvoux group in Dauphiné, while the inner, more continuous one extends from Monte Rosa to Gran Paradiso and Mercantour in Southern Piémont.’ A third, smaller, but continuous inner belt may be said to lie between the Dora Riparia and the Maira Valleys, with Monte Viso midway 1 In Piémont alone the crystalline schists, lying between the Mercantour massif in the south and Monte Rosa in the north, cover an area of 200 by 30 kilometres, or roughly 2,400 square miles, of which the three principal pietra verde masses represent about one-fifth. These masses are all composed ° of basie roeks, more especially of diorite, diabase, gabbro, serpentinous and hornblendic rocks. The white marble of Susa is, as shown above, Archean, in contrast to the Triassic marble of the Apuan Alps, but both attest the process of the deposition of coarse calcareous material being followed by that of gradually finer to very fine material purified by solution and precipitation. The majestic triumphal arch at Susa shows that the marble of that locality, as that of Carrara, was quarried already by the Romans. Similar saccharoidal limestone intercalations are also worked in the Pellice, Upper Po, and Varaita Valleys. I propose to refer to these and the pietra verde areas, as also to Franchi’s recent divergent views as to their age, in a subsequent paper. 2 GC. Diener outlines a similar series of belts in his Gebwugsbau der Westalpen, 1891, but embraces in his generalizations the entire ¢hain of the Alps. Sidney Melmore—The St. Bees Sandstone. 1% but outside the western edge, albeit this third belt forms more obviously part of the second one. The surface-level of the Permian zone varies between 2,000 and 1,000 metres altitude, the highest being at Montgioie and Chétif (Courmayeur) and the lowest near Modane and in the Doron Valley, while the parallel Archean zones vary in altitude between 4,000 and 3,000 metres. Itis therefore obvious that the Permian and concomitant zones must have been deposited in a longitudinal trough at a time when the Archean groups had already experienced a first partial raising, followed by a long period of erosion in the Lower Paleozoic interval. The marked unconformity at the points of contact between the Archean and the Paleozoic and Mesozoic formations warrants the same inference of a long intervening period of erosion. A further uprise, which also affected the secondary formations, appears, on similar grounds of unconformable superposition, to have taken place in post- Liassic,! and a third occurred in Miocene times, which last-named movement, proceeding, like the preceding ones, mainly in a radial sense from the south-east, viz. from the Mediterranean, probably imparted to the. Maritime and the Western Alps, as also to the Ligurian and Apuan ranges, their present general alignment and configuration. The initial emergence of the Montgioie and Apuan ranges as ellipsoidal groups probably occurred before that of the Apennines; but it 1s during the third and last great movement that the final uprise of the Permian schists, already more or less subjected to metamorphism and overlain by the younger formations, must have taken place in the Apuan Alps as the nucleus of that range, and as its average surface- level of about 1,500 metres above the sea is the same as that of the . analogous zone in the Maritime and Western Alps, it follows that the Permian formation in all the three ranges must have been raised to its present level simultaneously in Miocene times. V.—A CuHemican Examination or tHE Sr. Brees Sanpsrone oF West CUMBERLAND. By SIDNEY MELMORE. {J\HE following analyses were made to ascertain the magnitude of local variations in the St. Bees Sandstone of West Cumberland. It will be convenient for this purpose to consider the district as follows :— : _ The area south of St. Bees, as far as Calder Bridge. The area north of Maryport, as far as Wigton. 1. THe area sour or Sr. Buss. In view of its basin-shaped character, the observed dips in this area vary considerably in value and direction. On the whole, however, there is a constant dip to the south. 1 Of this post-Liassic uprise, followed by a period of erosion, evidence is afforded by a general and marked discordance between the strata of the Upper Lias and the Tithonian, and, again, between the Neocomian and Senonian both in the Western and in the Apuan Alps. DECADE VI.—VOL. IlI.—NO. I. 2 18 Sidney Melmore—The St. Bees Sandstone. The general character of the sandstone is so well known as to need Under the microscope, specimens from no further description here. this area exhibit a few cases of secondary deposition of silica on quartz. The average thickness of these secondary layers is about 0°02 mm. : West Newton xe x Jn Aspatria |° Maryport ty Flaiston : NN Gos forth Fic. 1.—Map of West Cumberland, showing localities mentioned in the text, with the observed dips. . Samples of this sandstone were taken from St. Bees Head, a quarry near the village of St. Bees on the road to Egremont, a quarry near Whinseales, Egremont, and from a quarry at Calder Abbey, near Full analyses were made of the samples from Calder Bridge. St. Bees Head and Calder Abbey as representing the northern and southern portions of the area respectively. Sidney Melmore—The St. Bees Sandstone. 19 The results are as follows :— Ile iste SiQ2. : ; i; A 83-99 85-96 Aly O3 5 , 5 ; 8-37 6-93 Fes O3 3 j 5 ; 1-61 1-36 He On mae. : i F none none Mn O2 4 R i ‘ none , none CaO. } P : : 0-49 _ 0-49 MgO i b : é 0-26 0-11 KO. ; , d ; 3-412 2-844 Naz O t : : ‘ 1-253 0-70 CQ.. : ; P 0-026 0-026 Hz» O (combined) F : 1-11 0-723 Sulphuric acid (S Os) : 0-31 0-32 100-831 99-463 I. St. Bees Head. II. Quarry at Calder Abbey. 2h CA %, % &, Age We, Combined. Weter —— : Sulphuric Acid --------- Fic. 2. The amount of combined water in the samples from St. Bees Quarry and the quarry at Whinscales was also determined, as also the iron at the latter place. The percentage of combined water and sulphuric acid are stated graphically in Fig. 2, as by this means the variations are more easily seen. The amount of ferric oxide is fairly constant, but shows a slight increase towards the northern end of the basin. The total alkalis show a marked increase in this direction. 2. THe AREA NoRTH oF Maryport. The remarks on the tectonics of the southern area apply also to this northern basin, but the constant dip is to the north. Samples were taken from quarries on the coast at Maryport, from a quarry at Hayton, from the West Newton Quarries, and from a quarry at Red Dial near Wigton. Fewer cases of secondary silica were noticed in the specimens from this basin, but when they occurred they were of the same order of magnitude as those in the southern basin. The amount of combined water was determined in the samples from Hayton and Wigton. The value of the combined water at Maryport is somewhat less than that of St. Bees, but it rises steadily to a maximum near West Newton, and then begins to decrease. 20 Sidney Melmore—The St. Bees Sandstone. Full analyses were made of the Maryport and West Newton samples; the results are :— Ii. Vs SiQ2. ; , ‘ : 86-57 84-58 Aly Os , : : : 6-50 7-21 Fes O3 : : : , 1-92 - 2-05 FeO. : ; ‘ none none Mn O2 ni ; 5 i none none CaO. ; : : ; 0:57 1-40 MgO : : : : 0-083 0-098 K,0O. 5 : : : 1-618 1-376 Nag O : ; : j 0-574 0-392 COQ.. : 0-078 none HO (combined) ; i 1-042 1:72 Sulphuric acid {S Os) : 0-285 0-345 99-240 99-171 III. Sample from Maryport. IV. Sample from West Newton Quarries. The percentage of ferric oxide continues to increase from the value found at St. Bees till it also reaches a maximum near West Newton, and then decreases in value. The percentage of S O, rises slightly in a northerly direction, its amount, however, being practically the same . for both basins. The total alkalis gradually decrease in the same direction. Conctusions. Considering each basin separately, all the localities where samples of sandstone were taken lie practically along the strike of the rock. The percentage of constituents found in these samples are therefore functions of the same geological horizon, and differ among themselves by virtue of their representing samples taken from different points of this horizon. The results therefore show superficial variations, rather than variations in geological time. It is well known that the process of kaolinization is accompanied by the formation of combined water, and this water 1s produced quantitatively in proportion to the kaolin. The degree of kaolinization can therefore be estimated with considerable accuracy by determining the amount of combined water in any sample of sandstone and correcting the value found for the presence of such other hydrated compounds as gypsum (Mackie, Trans. Edin. Geol. Soc., vol. vii, p. 454, 1899). In the present connexion, the values of combined water plotted are uncorrected for combined water in CaS O,.2H,0, as the amount of calcium sulphate present in the seudeband is practically constant. Any alteration in the shape of the curve would be very slight if such a correction were applied. The substances whose presence is essential to kaolinization are water and carbon dioxide. In sea-water the amount of dissolved oxygen varies from about 1 to 3 c.c. per litre, and the amount of carbon dioxide from 2 to nearly 40 c.c. per litre. The gaseous contents of sea-water increases with the depth to about 2,000 feet, below which depth the water contains scarcely any dissolved gases. Assuming kaolinization to have proceeded under these conditions J. Wd ackson—Brachiopod Morphology. sli below the surface of the sea, and to have given rise to the amount of combined water found in the different samples of sandstone, we can arrive at the comparative depth of the various points in the basin where analyses have been made. A section through the St. Bees basin from Calder Abbey to St. Bees will thus show a maximum depth at a point almost midway between St. Bees and Whinscales, the depth decreasing north and south. Similarly, in the northern basin the maximum depth is attained a little north of West Newton, and decreases more rapidly to the south than to the north. Thus both basins were steeper at their southern extremity than at their northern. The depth of the basin at Maryport was not very great ; in fact, we have evidence in the form of ripple-marks of littoral conditions at this place. VI. —Bnracuiopop MorrHotocy: Norrs ann Comments on Dr. J. Auttan THomson’s PAreErs. By J. WILFRID JACKSON, F.G.S., Assistant Keeper, Manchester Museum. )\ROM a long and careful study of the Brachiopoda I am led to offer some observations upon the two recently published papers by Dr. J. Allan Thomson which have appeared in this Magazine.} In the case of Dallina I cannot agree with Dr. Thomson regarding the type of folding. He considers D. septigera (the genotype) and D. raphaelis as dorsally biplicate, D. floridana as dorsally uniplicate. Now dorsal biplication is brought about by the dorsal sulcus being superimposed upon a single dorsal fold. In D. septigera, as well as in D. floridana, a broad ventral sulcus is superimposed upon a dominant ventral fold ; these two species, therefore, are, in my opinion, ventrally biplicate (as in Magellania flavescens and some others). This confusion of folding has led Thomson to question the generic position of Zerebratula grayt, Dav., which was also referred to Dallina by Beecher.? This is a ventrally uniplicate species with alternate multicostation, and according to Thomson cannot belong to Dallina. He further states that ‘‘ there seems to be no difficulty in referring it to Magellania, as it apparently possesses the Magellaniform hinge- plate and cardinal process”. ‘There is some mistake here; the hinge-plate is not Magellaniform. Davidson’s figure ? is misleading. There is no hinge-plate such as occurs in the genotype of Magellania (I. flavescens). A mesial septum is present, extending from about the middle of the dorsal valve to near the apex, where it merges with slight bifurcation into a thick deposit, on the floor of the valve. _ From each side of this deposit the dental sockets and crural bases arise ; the cardinal process is transverse and weak. Apart from this * “Brachiopod Morphology: Types of Folding in the Terebratulacea,’’ GEOL. Mac., Dec.- VI, Vol. II, February, 1915,-pp. 71-6; ‘‘ The Genera of Recent and Tertiary Rhynchonellids, ” ibid., September, 1915, pp. 387-92. 2 “* Revision of the Families of the Loop- “bearing Brachiopoda » and ‘‘ The Development of Terebratalia obsoleta, Dall’?: Trans. Conn. Acad. Arts and Sei. -, 1x, pp. 376-99, pls. i, ii, 1893. aes Monograph of Recent Brachiopoda’’: Trans. Linn. Soc. London ; ae (2), iv, pl. x, fig. 3, 1886-8. 22 Dey ian ackson—Brachiopod Morphology. T. grayi cannot be referred to Magellania, or even to Dallina, on account of the ventral valve possessing dental plates in the form of strong buttresses with a small recess behind each. Dental plates are entirely absent from Magellania throughout life, and also from Dallina septigera and D. floridana, so far as the adult stages are concerned, but according to Fischer & Oehlert! the teeth of the ventral valve in D. septigera are supported in a young state by dental plates. These become attenuated with age and disappear entirely in the adult. TZ. grayi, therefore, is in need of a new generic name, as it cannot be referred to Zerebratalia even, on account of the loop being in a higher stage of development. ‘The name Zhomsonia, therefore, is now proposed for this form. ; Let us now turn to Zerebratalia. This genus was founded by Beecher? on Terebratula transversa, G. B. Sowerby, a ventrally uniplicate shell, but, as Thomson points out, the actual species on which Beecher established a different ontogenetic series from that of Terebratella s.str. was Terebratella obsoleta, Dall. Thomson considers this latter species to be a dorsally uniplicate form, and on this account creates a new genus—Dallinella—tfor its — reception. Beecher’s outline drawing of 7. obsoleta* is very misleading, and gives a very erroneous idea of the type of folding. Dall’s figure * is also of little service as it is only a dorsal view, but his description is very clear. I possess a specimen which agrees exactly with Dall’s description, and shows the true folding to be undoubtedly ventrally biplicate. ‘he anterior margin of the shell has much. the same appearance as in some specimens of Magellania flavescens.© The teeth of the ventral valve are supported by dental plates which are rather more definite than in Zerebratalia transversa and Thomsonia grayt.® In the dorsal valve the cardinalia is of the same weak character as in the two species just mentioned. The species, therefore, seems to me to be rightly placed in the genus Zerebratalia. Thomson further suggests that 7. transversa, Sow., and 7’ coreantca, Adams & Reeve, are true Zerebratella, and if so Terebratalia becomes a synonym of Torebratella. T. coreanica agrees with ZT. transversa and Thomsonia grayi in having the same type of dental plates and weak cardinalia, except that the cardinal process is somewhat more definite. Like Thomsonia grayt there is a callous deposit in the umbonal area. This species and 7. ¢ransversa cannot, therefore, be separated from the genus Terebratalia. Such structural features as dental plates are, in my opinion, worthy of more consideration than has been given them in the identification and description of species. They are not only helpful 1 Hxpéd. Scient. du ‘‘ Travailleur’’ et du ‘‘ Talisman ’’, 1880-3, Brachio- podes, Paris, 1891. 2 Op. cit., p. 382. 3 Op. cit., pl. ii, figs. 6-9. 4 Proc. U.S. Nat. Mus., xvii, pp. 726-7, pl. xxx, fig. 7, 1895. 5 See Davidson, op. cit., pl. vii, figs. 6b, 10. 6 The dental plates in both these are very similar, and appear to have been overlooked in descriptions of the species. J. W. Jackson—Brachiopod Morphology. 23 in defining genera, but their presence or absence is also an important character separating the two sub-families Magellaninee and Dallinine. ' They appear to be entirely absent from the Magellanine, but are always present in the true Dallinine, even in fossil ; genera referred to this group. The generic position of Zerebratula spitzbergensis, Dav.,is not easy to define. It possesses very definite dental plates which are more vertical than those in MMacandrevia. he cardinalia, however, is not unlike that of Dallina septigera and floridana, i.e. typically Magellaniform. With regard to Zerebratula frontalis, Midd., this possesses somewhat obscure dental plates much as in Zerebratalia. Its loop development and cardinalia suggest relationship with the Terebrataliform stage of Macandrevia cranium as figured by Beecher.’ Regarding the Cincta-like forms referred to Laqueus, the following notes, based on four of the species, may be of some interest :— These species fall into two groups according to the character of the cardinalia. Lagueus pictus (Chem.) and LZ. rubellus (Sow.) possess obscure dental plates curving back to the apex of the valve. The hinge-plates in both are almost similar, consisting of two divergent buttresses rising from the floor of the valve and forming the dental sockets and crural bases. In Z. pictus these buttresses are divided clear to the apex, where a small bilobed cardinal process is present. In ZL. rubellus there is no cardinal process, the divaricator muscles being attached directly to the apical parts of the buttresses. Each species possesses a slight mesial septum which in old specimens is superimposed on a broad and massive base with deep muscle imprints on each side. L. californicus (Koch) and B. blanfordi (Dunker) have better defined dental plates, which are almost vertical in the latter. The dorsal valves of both possess Magellaniform hinge-plates (as in Mf. flavescens); there is no cardinal process. L. blanfordi is the nearest to Cineta in outward appearance, as the interior margin is strongly indented. None of my specimens of ZL. californicus show the ventral plication as given by Davidson,? but only a tendency towards a truncated front. Possibly Davidson’s figure is incorrectly drawn. The relationship of this Cincta-like group to the remainder of the Dallinine is difficult to decide. The peculiar double attachment of the loop suggests a complete divergence from the general line of Macandrevian development. Dall, in 1895,° proposed Frenulina for the A. sanguinea, Chem. Points of difference in the early stages of loop development, together with the presence of dental plates in one and their absence in another, seem good ground for the separation of these two, forms into different sub-families, Mihlfeldtia truncata being placed in the Magellanine and Frenulina sanguinea remaining in the Dallinine. The adoption of this course would necessitate the changing of the term Mihlfeldtiform stage in the Dallinine to Frenuliniform stage. One remarkable point of difference in the development of the loop in I. truncata is clearly seen in the figure given by Fischer & Oehlert* of an early stage of this species. Here the loop is strikingly like the early stage of Tvrebratella dorsata, figured by Beecher.* There appears to be no stage like this in the Dallinine, where the descending branches of the loop appear early and are connected, thus forming a complete primary loop, whereas a feature of the Magellanine is the development of a secondary loop in the middle of the valve on the top of the septum, before the appearance of the primary lamelle. Deslongchamps’ figure ® of a young example of H. truncata, 2mm. in length, also shows a condition of loop somewhat similar to that of an adult Uegerlina lamarckiana (another member of the Magellaninz) figured by Beecher.” Some difference, however, is presented by the former having the ascending branches united to form a ring, whereas in 1. lamarckiana the ring is incomplete.” The loop of Frenulina sanguinea, on the other hand, passes through early stages exactly like those of Macandrevia cranium. RHYNCHONELLIDS. In describing the manner in which the delthyrium of Hemithyris becomes partially closed, Thomson ” calls attention to a curious plate on the inner side of the apex of the pedicle valve. This plate, a kind of continuation of the deltidial plates, is free in front and separated from the shell by a narrow cavity. This feature, which I have termed the ‘‘pedicle collar’? in my forthcoming report on the 1 “* Revision,’’ etc., pp. 383-4. * Mon. Perm. Foss. England (Pal. Soc.). Journ. de Conchyl., xxviii, p. 240, 1880. Amer. Journ. Coneh., vi, p. 129, 1870. Not 7. pectunculus, Schl. ; see King, op. cit., p. 245. Op. cit., p. 724. Op. cit., pl. vii, fig. 1lw. Op. cit., pl. i, fig. Da. Copied by Davidson, op. cit., p. 106, fig. 9. 10 Op. cit., pl. i, fig. Db. 11 See also Davidson, op. cit., pl. xxi, fig. 11. 12 Op. cit., p. 390. ao ty Ona fF © J. W. Jackson—Brachiopod Morphology. 25 Brachiopods of the Terra Nova Expedition, is not by any means peculiar to the Rhynchonellids. It is present in Liothyrina, Terebratulina, and in all the short-looped forms I have been able to examine, some twenty-four recent species. It is also present in several fossil forms, including the large Crag fossil Zerebratula grandis, T. bisinuata from the London Clay, and Cyclothyris latissima from the Lower Greensand of Farringdon. In Terebratulina cancellata, Koch, the pedicle collar is strongly developed, and forms a perfect tube extending forward for some little distance, whilst in Megathyris decollata, Chem., it is well-developed and is supported by a sharp mesial septum. It is a structure which grows larger as the shell increases in size, and is the ‘‘doublure sous-apicale’’.and ‘‘doublure sous-cardinale’’ of Fischer & Oehlert.? Judging from my own collection the pedicle collar is never developed in the higher long-looped forms; it is entirely absent from the following genera: Jlagellania, Terebratella, Dallina, Macan- drewia, Terebratalia, Laqueus, and Frenulina (type sanguinea). In some of these, however, there is occasionally a thickening in the umbo around the foramen assimilating a pedicle collar, but it is fused to the shell and never free anteriorly.’ _In the lower genera referred to the family Terebratellide a curious feature is present: Jlihlfeldtia truncata and Megerlina lamarckiana both possess a pedicle collar, but Araussina rubra does not; it only has a thickened plate fused to the floor of the umbonal cavity. Genus rHerA,’ Thomson. With regard to the relation of Rhynchonella lucida, Gould, to Thomson’s new genus thea, I possess a specimen of this form and find that it possesses fairly strong dental plates. This fact, together with the hypothyrid character of the pedicle passage, excludes the species from Atheia. Like Hemithyris psittacea there is no true cardinal process in the dorsal valve, the divaricator muscles being attached to the posterior ends of the crural bases. _ The absence or presence of a cardinal process in Rhynchonellids seems to be a matter upon which some difference of opinion exists. In H. psittacea I have failed to find any structure iba ees to a true cardinal process, but in two large adult specimens of ‘ Hemithyris’ nigricans in my collection from Chatham Islands there is a small but distinct transverse bilobed cardinal process extending outwards like a shelf from the apex of the valve; the mesial septum in these specimens is also much stronger than in H. psittacea. In the ventral valve the dental plates are recurved towards the apex and net vertical as in H. pszttacea. Regarding dental plates, etc., a close study of the fossil fering of the nigricans group would no doubt reveal some interesting features. The Manchester Museum possesses three specimens belonging to this group from the Table Cape Beds at Wynyard, Tasmania. One of these specimens is apparently closely related to H. nigricans; the 1 Hxpéd. Scient., pp. 44, 108, ete. 2 In old adult shells of Hemithyris psittacea the pedicle collar sometimes becomes fused to the floor of the umbonal cavity of the ventral valve. 26 Professor Percy Kendall—Glacier Lake Channels. surface of the valves is ornamented with about thirty ribs, which are rather more angular and squamose than in typical nzgricans ; a mesial septum is also visible through the shell of the dorsal valve. Without spoiling the specimen it would be impossible to study the internal characters. The two other specimens, one broken, the other perfect, are quite distinct from that described. The valves are ornamented by about forty-six radiating coste, increasing by bifurcation. The cost are divided by moderately deep furrows and are surmounted by short tubular spines which are arranged concentrically, following the growth-lines. The dimensions of the perfect specimen are as follows: length 16°5mm., breadth 19 mm., depth 7°5mm. ‘The imperfect example represents a shell of approximately the same size, and is interesting as it exhibits the internal characters. The teeth of the ventral valve are supported by very distinct dental plates, which ditfer entirely from those of H. nigricans by being almost vertical and more like those of H. psettacea. The foramen is rather large and the pedicle collar somewhat weak, as are also the deltidial plates. The dorsal valve possesses a thin mesial septum extending to the apex, while the dental sockets and crural bases are more divergent than in H. nigricans and psittacea. No cardinal process is visible. I am unable to identify the above species with accuracy owing to the absence of specimens for comparison, but it seems to be related to Rhynchonella squamosa, Hutton = calata (M‘Coy MS.), Woods = pyxidata (Watson MS.), Davidson. Hemithyris imbricata, Buckman,’ from the Miocene-Oligocene beds of Cockburn Island, off Graham Land, Antarctica, is near to it in general appearance, but this species appears to possess no dental plates. Another species possessing some resemblance to the one under discussion is Rhynchonella (?) tubulifera, Tate,* from the Oligocene of Muddy Creek, Victoria. VIl.—Guactrr Lake CuHannets. By Percy Fry KENDALL. N 1902 I published a paper,? the outcome of several years’ observation, on certain phenomena associated with the glacial deposits of the Cleveland area, which I attributed to the former presence of a series of temporary lakes and lakelets upheld in the recesses of the hills by the margin of a great ice-sheet occupying the greater part of the North Sea. This interpretation met with so wide an acceptance, even by those geologists familiar with the district who had previously attributed the glacial deposits to a marine origin, that during the succeeding thirteen years I have steadfastly refrained from replying to criticism, hoping by this abstention to keep the issues unclouded by a controversy that might at any stage develop an acerbity not always lacking in earlier discussions. 1“ Antarctic Fossil Brachiopoda, etc.’’: Wiss. Ergebn. Schwed. S.P. Exped., 1901-3, Bd. iii, No. 7, 1910. 2 Trans. Roy. Soc. S. Australia, xxiii, p. 257, 1899. 3 Q.J.G.S., vol. lviii, pp. 471-571. Professor Percy Kendall—Glacier Lake Channels, 27 Professor Bonney has favoured me with a copy of a pamphlet! in which he subjects my views to a criticism based upon a careful examination of parts of the area. Not content with mere destructive criticism, he elaborates in some detail an alternative explanation. The whole paper is so moderate, and the author’s appreciation of my work so generous, that I must break through my self-imposed rule of silence, and this I do the more willingly as no other critic has ventured to suggest any other hypothesis. I may briefly recite the phenomena to be explained. A great series of sharply-cut ravines, in some cases veritable gorges, traverses the country, either within the area occupied by glacial deposits or just beyond its margin. ‘Their transverse section closely resembles that of a railway cutting, with which Professor Bonney aptly compares them ; there is the steep ‘batter’, the flat floor, and, let it be particularly noted, a comparable sharpness in the angles at the top and bottom of the slope. Sinuous channels have a steep batter on the outsides of bends, and gentler slope on the inside curve, just as we find in the ease of the banks of a river, though not commonly of a river valley. I draw two inferences from these features: (1) that the channels were excavated rapidly by a volume of water sufficient to occupy the whole floor, (2) that their formation was so recent that denudation has done little to modify the original contours. As regards situation, they are found cutting through watersheds, even the main water- parting of the whole district (e.g. Newtondale), and sometimes trenching. boldly projecting spurs. Often a succession of spurs are cut along a line, as though an originally continuous ¢ehannel had been segmented up by the development of cross-contour valleys of normal type. A feature which opposes this interpretation is that, instead of the fall-line constituting a continuous gradient from end to end of the series, the outfall level of one segment generally coincides with the intake-level of the next, even though a distance of a mile or two may intervene. This arrangement is explicable on the supposition that the intervening space was occupied ‘by the standing waters of a lake, but is difficult to reconcile with an original continuity of the channels. Similar relations have been observed in many parts of Scotland and of the North of England. Another significant arrangement is that which I have called a ‘* Parallel Sequence ’’, that is, a series of parallel channels cutting at successively lower levels a single spur. They fall in the same direction, and there is a method indicated by their relative heights ; each channel, as a rule, commences to break the ridge-line of the spur at almost the exact level of the intake of the next higher channel, as though—this is my explanation—the channels drained a lake held up by an ice-barrier, and when the ice withdrew so as to uncover a slope below the intake level, the drainage was diverted and the formation of a new channel begun. In some cases six, eight, or even more channels traverse the same spur in a distance of a mile or two. No comparable case of river-capture is known to me, and I am unable to imagine conditions which would produce such an effect. The 1 On certain Channels attributed to overflow streams from ice-dammed lakes. 28 Professor Percy Kendall—Glacier Lake Channels. systematic disposition of the channels is still more comprehensively exhibited when a larger area is embraced in the review. The Cleveland area illustrates this fact with admirable clearness, for which reason I entitled my description ‘‘ A System of Glacier-lakes in the Cleveland Hills”’. On the northern face of the hills I found evidence of a series of lakes draining, some to the westward of a dividing-line by a set of lake-to-lake channels into a lake in upper Eskdale; another set draining eastward to a main overflow by which they discharged into the samelake. The lake in Eskdale was, I supposed, upheld by a lobe of ice that stood across the Esk, leaving a mass of boulder-clay near Lealholm as a species of moraine. I may remark in passing that, as Professor Bonney no doubt observed when he visited the place, this supposed moraine divides the Esk Valley into two parts of surprisingly different topography, the upper part characterized by enormous terraces of ancient (lake-)alluvium, and the absence of any boulder- clay hills or other characteristic glacial features, as well as of gorges. along the course of the river; while, below this obstruction, the tumultuous heaps of boulder-clay and other Drift deposits, and the succession of gorges through which the river passes form a contrast as complete as could be desired to the tamer river-scenery of the higher reaches. The ice-lobe similarly obstructed the tributary valleys on the south side of Eskdale, and not only are there masses of boulder-clay obstructing their lower ends and producing topographic contrasts. comparable with those of the main valley, but the spurs are trenched by channels by which the lake-waters evaded the obstacles. To. complete the series these channels conducted to a lakelet near Goathland, and thence across the main Cleveland watershed by the giant trench of Newtondale into the Vale of Pickering. Space does not permit me to discuss in full detail the whole system, and it would be hardly fair to my courteous critic to evade the issues specifically raised by him. I will therefore confine my attention to one district of which his knowledge is almost as recent and probably as. full as my own, viz. the country between Fen Bogs, near Goathland, and the Esk Valley at Egton Bridge. The interested reader will find it fully pourtrayed in the map with 25 ft. contours in my paper already referred to (pl. xxii), or, better still, in the Proc. Yorks Geol. Soc., 1903, pl. vi. The general build of the country is fairly simple—the axis of the main Cleveland anticline runs W.-KE., about through Julian Park. The River Esk flows along an inflection of the northern slope of this fold. The Murk Esk, a tributary of the Esk, rises by two heads, Eller Beck and Wheeldale Gill, from the south side of the anticline, and these streams, after flowing for distances of one and two miles. respectively towards the south, recoil from an opposing escarpment and swing round across the anticline—a very clear case of ‘stream trespass’, as Fox Strangways showed. The ‘ certain channels’ in this area are—(1) Two parallel trenches on Murk Mire Moor, beginning as open notches on the bold scarp over- looking the Esk Valley within a mile or a mile and a half of the Professor Percy Kendull—Glacier Lake Channels. 29 river, and respectively 450 and 600 feet above its level. ‘hey cut across a prominent spur and then coast along it fortwo or three miles, and finish almost as inconsequently as they began. (2) A headland, Two Howes Rigg, separating Wheeldale Gill from Eller Beck, is trenched by achannel about a mile long that carries on the chain to within about a mile of the beginning of Newtondale, a tremendous ravine that attains a depth of 250 feet where it passes through the escarp- ment formed by the Kellaways Rock. Professor Bonney regards these ‘ channels’ as relics of a very ancient river system that has been encroached upon by a more energetic system, namely, that of the Murk Esk. In my first attempts to elucidate the river development of the Cleveland area I attributed the principal role to river-capture, and presented it for discussion at a meeting of the Yorkshire Geological Society, but later, when I descended to details, I found insuperable difficulties, and I think Professor Bonney will recognize their importance. Firstly, the lower channel on Murk Mire Moor—as I have mentioned, begins with a perfect railway cutting section within one mile of the River Esk and 450 feet above it. The floor falls, not towards the river, but away from it, with a fairly steady gradient except for accumula- tions of peat and a small amount of running down of the sides. The upper channel falls in the same direction, and the channel on Two Howes Rigg continues the course, but from west to east. After ashort interval the great gorge of Newtondale, falling south, com- pletes this series. I ask, is it likely that two rivers could have flowed backward across the Cleveland: anticline and away from the Esk, the main drainage line of the district ? Their sections, as [ have pointed out, indicate that they carried a large volume of water. Whence was it flowing? Several alterna- tives might be suggested—(1) That the channel had been deprived of its headwaters by the widening of the Esk Valley. This, unless the course of the Esk has been materially altered, would increase the drainage by one mile, and then only on the assumption of a vertical side to the Esk Valley. (2) That the Ksk itself flowed this way and cut the Newtondale channel as well as those along the Moor-edge. Such a readjustment of drainage is not only opposed to the whole build of the country, but it seems negatived by the behaviour of Wheeldale Beck and Eller Beck, which shows that the ‘trespass’ was all in the opposite direction (i.e. encroach- ment across the anticline by the Esk by virtue of the ‘law of steepest slope’). (8) That there was no Esk Valley at the time when these channels were operative and that the drainage of the North Cleve- land hills, ignoring syncline and anticline alike, came over into this system. Ido not think such a hypothesis needs any refutation, for Professor Bonney expresses the opinion that the original watershed was ‘‘rather more than a quarter of a mile north of Goathland Station”. This is almost exactly on the axis of the anticline. A watershed in such a position would, however, attach the Murk Mire Moor channels to the Esk drainage, although they slope directly away from it. (To be continued.) 30 Notices of Memoirs—A. Coa—Ordovician, Cader Idris. NOTICHS OF MEMOTRS. I.—Tue Orpovictan Srquence In THE Caper Jpris Disrricr (MerionetH).1 By Arrnur Husperr Cox, M.Sc., Ph.D., F.G.S., and ALFRED Kinestey WELLs. EFERENCE was made to the work of previous observers, including Sedgwick, Ramsay, Cole and Jennings, Geikie, and Lake and Reynolds. The Cader Idris range is formed by a great escarpment of Ordovician igneous rocks, facing northwards across Barmouth Estuary towards the Harlech dome.. The igneous rocks were for long regarded as being all of Arenig age. Re-examination of the area has shown the presence of four distinct volcanic series among the Ordovician rocks, and the following descending sequence has been established— f 10. Talyllyn Mud- Grey blue-banded mudstones with Glenkiln-Hartfell . stones Amplexograptus arctus in the ( lowest beds . - . 800 ft. 9. Upper Acid or ‘Andesitic’ and rhyolitic ashes Craig-y-Llam and lavas . - 900-1,000 ft. Series 8. Llyn Cau Mud- stones 500 ft. 7. Upper Basic or Pillow lavas (spilites) with tuff and Pen-y-Gader chert bands ; . 3800 ft. Series Glenkiln with Upper } 6. Llyn-y-Gader Blue-grey mudstones with thin Lilanvirn Mudstones adinole -like bands and with and Ashes massive ashes above and below 450 ft. 5. DarkMudstones Frequently containing pisolitic ivon-ore . ‘ oats 4. Lower Basic or Pillowy spilitic lavas with inter- Llyn Gafr calated ashy and shaly bands, Series massive banded andagglomeratic ashes at the base . 1,500 ft. ° 3. Didymograptus Dark slates with well-marked ash Lower Llanvirn | bifidus Beds bands in the lower portion 500 ft. 2. Lower Acid or Rhyolitic ashes with some slates MynyddGader above, rhyolitic lavas below Arenig . : : Series 300 ft. 1. Basement Beds Striped arenaceous flags and grits 100 ft. Unconformity Upper Cambrian . Tremadoc Beds Both acid and basic rocks occur as sills at numerous horizons. The basic rocks are diabases of various types, all with the felspars considerably albitized and usually with primary quartz. The acid rocks are soda-granophyres. The granophyre intrusions cut and are later than the basic intrusions, and locally hybrid rocks appear to have been formed along the junctions. No basic intrusions have been found above the Upper Basic Volcanic Series, and no acid intrusions above the Upper Acid Series, and it is noteworthy that the 1 Read before the British Association, Section C, Manchester, 1915. Notices of Memows—Prof. Wallace—Brines of Manitoba. 31 granophyres appear to be closely related to the extrusive rhyolites among which they are intruded. This fixes an upper limit to the age of the diabases in this district. The various beds strike more or less east to west, and dip steadily southwards at about 40° until the Talyllyn Mudstones are reached, when folding and rolling of the beds immediately begin. Two N.E.-S.W. shatter faults—the Dolgelley and Talyllyn faults—cause a certain amount of repetition, and give rise to the Dolgelley-Llyn Gwernon and to the Talyllyn Valleys, the former to the north and the latter to the south of the escarpment. A strike-fault between Mynydd Gader and Cader Idris cuts out the whole of the Bifidus Beds, bringing the Lower Acid and the Lower Basic Volcanic Series against one another. The intrusive rocks frequently cause local variations in the dip and strike. All the softer strata are strongly cleaved, so that fossils are difficult to obtain. The slates within the Lower Acid Series have yielded a few extensiform graptolites, while from the Bifidus Beds the characteristic fossils were obtained at numerous localities. The D. murchisont zone has not been recognized by the authors, its place presumably being occupied by a part of the Lower Basic Series. The dark mudstones among which the pisolitic iron-ore is developed have yielded rather obscure graptolites, which, however, indicate a fairly high horizon in the Llandeilo Series. The presence of Amplexograptus arctus and Glyptograptus teretiusculus var. euglyphus in the lowest beds of the Talyllyn Mudstones indicates a high horizon in the Glenkiln, or, in other words, a low horizon in the Caradocian, and suggests that the immediately underlying Upper Acid Series is at approximately the same horizon as the Snowdonian volcanic rocks of - Conway. This youngest of the four volcanic series on Cader Idris is therefore considerably higher in the Ordovician than has been previously supposed. The position of the boundary between Cara- -docian and Llandeilian has not yet been established, owing to the unfossiliferous character of the blue-grey mudstones of Llyn-y-Gader and Llyn-Cau. One of the authors (A. H. Cox) is indebted to the Government Grant Committee of the Royal Society for a grant which has partially defrayed the expenses involved in the investigation. The area is being mapped on the 6 inch scale. II].—Tne Corrostve Acrion oF CERTAIN Brines In Maniroza.’ By Professor R. C. Wattacr, M.A., Ph.D., B.Sc. RINE springs issue from Middle and Upper Devonian limestones. and dolomites at the foot of the Manitoba escarpment. At least eighty brine areas are known, with a total flow—during the dry season—of approximately 500 gallons per minute. The water circulates in the Dakota Sandstone, the basal member of the Cretaceous series, and extends laterally into the Devonian calciferous formation, from which it leaches sodium chloride, disseminated through certain dolomite horizons. The composition of the brines, 1 Read before the British Association, Section C, Manchester, 1915. 32 Reviews—Professor A. Keith—Antiquity of Man. expressed in percentages of total solids, is very similar to that of sea-water. It is a somewhat purer solution of sodium chloride, and also a more concentrated solution, than sea-water, the percentage salinity being 5-7 (sea-water 3:5). The salt-flats where the springs reach the surface are devoid of vegetation and studded with ice-carried boulders. These are representative of the pre-Cambrian igneous series of North-Central Canada—granites, gneisses, and epidiorites. They have suffered intense chemical disintegration, large boulders having been reduced to half their original size. Different minerals have been affected to different extents, but not even quartz or garnet has escaped corrosion. Ferromagnesians have been most intensely affected; and gneissose structures, hardly noticeable on unweathered surfaces, stand clearly revealed. The striking difference between the action of these brines and that of sea-water calls for explanation. Thin crusts of salt gather, during the summer months, on the flats and around the boulders. The salt is somewhat deliquescent ; and thin films of brine are drawn, by surface tension, over the surface of the boulders. Water in contact with the atmosphere is a powerful disintegrant. Alkalies are removed as chlorides or carbonates, and silica and alumina are precipitated as gels, separately or in com- bination. The gels exercise selective adsorption on the salts of the brine, alkali being taken up and the brine being left richer in the acid radicals. The brine is thereby rendered a more active dis- integrating agent, and the process goes on continuously. ‘The function of the dissolved salts is considered to be twofold: (1) they provide a thin film of liquid in contact with atmospheric oxygen ; (2) owing to partial adsorption by colloids, they provide an acid residual solution, which is a powerful corrosive agent. The evidences of the corrosive action of sea-water on beach boulders are no doubt obscured by mechanical attrition due to wave action.. Such corrosion cannot, however, be compared in intensity with that of the brines. Boulders between high- and low-water mark are alternately submerged and dry to the base—a state of affairs inimical to the persistence of thin films of liquid on the surface of the boulders. The initial conditions are consequently wanting ; and the relative immunity of beach boulders from chemical corrosion is due, not to any inability of sea-water to act as a corrosive, but to the absence of favourable conditions for the activity of the solution. REV LHwsS- I.—Tue Antiquiry or Man. By Artuor Kerra, M.D., F.R.S. pp. 519, with 189 text-figures. London: Williams & Norgate, 1915. Brace 10s. 6d. net. fP\HE subject of the antiquity of man seems naturally to fall to the geologist, with such aid as he can obtain from the human anatomist and archeologist. The value of the evidence which has to be considered can only be estimated by one who has a practical acquaintance with geological problems in the field. From Lyell onwards, therefore, all the most important works dealing with the Reviews—Professor A. Keith—Antiquity of Man. 33 question have been written by geologists; and he is indeed a bold man who would form independent judgments on the materials taken at second hand. Now, however, a distinguished human anatomist has entered the field, discussing the antiquity of man from his own point of view and trusting to such quotations from geological literature as suit his purpose. We therefore turn with great interest to Professor Arthur Keith’s handsome volume which has just been received. Professor Keith writes in an attractive style, and though at times his matter is somewhat technical his explanatory figures are so numerous and clear, placed as they are in frames of standard magni- tude, that even the non-anatomical reader will find no difficulty in appreciating his points. His story, indeed, is that of an eager student ever searching for the meaning of things, and it gives an excellent idea of the aims and methods of modern physical anthropology. Our only regret is that lack of a geologist’s caution permits him to make dogmatic statements about the age of the various remains in terms of years, which will doubtless give gratifying satisfaction to an unwary public, but will also deceive them in an unfortunate manner. Professor Keith begins with Neolithic man, and shows that he differs in no respects from the men of Europe at the present day. His description of the discovery of his remains in the megalithic monument at Coldrum, Kent, is a good example of his picturesque writing. We hardly appreciate the comparison of this monument, however, with the Sardinian ‘giant’s tomb’, when the relative proportions and positions of the stones have to be so much altered to make it plausible (cf. figs. 3 and 9). Proceeding to Paleolithic man, Professor Keith shows, from the well-authenticated cases of Paviland, Engis, and Cro-Magnon, that at least the later races were also similar to those of modern civilized man. He then soon begins to illustrate the disadvantage of his _ position by accepting as valid evidence a series of human remains, ot which scarcely any—perhaps none—can be regarded with certainty as belonging to the age of the stratum in which they occurred. He even continues to believe that the Galley Hill man dates back to the Chellean period, and thinks that the Ipswich man may be earlier. Thus he assigns a much greater antiquity to modern man than a cautious geologist or paleontologist would be disposed todo. In fact, he introduces unnecessarily an anomaly into the series of undoubted fossil human remains which accord with paleontological theory and expectation. Of these undoubted fossil remains Professor Keith gives an excellent account, enlivened by his own observations, and treats in succession of Neanderthal man, Heidelberg man, Pithecanthropus, and Koanthropus. The discussion of the latter genus, or Piltdown man, is especially interesting, and occupies no less than 200 pages. The precise result is a little obscure, but Professor Keith now admits that the chimpanzee- like lower jaw was correctly restored by the paleontologist, and he has considerably reduced his original estimate of the size of the brain-case, which he thinks cannot have exceeded 1,400 c.c. We can only express the hope that Mr. Charles Dawson will continue his DECADE VI.—VOL. III.—NO. I. 3 34 Reviews—Prehistoric Archeology. researches in the Piltdown gravel, and discover more nearly complete specimens which may solve some of the problems that still remain inexplicable. IJ.—Preuisroric Arco Z0LoGyY.! ial the first paper in the list Professor McKenny Hughes deals with flint, its origin and destruction, and the extent to which chipped flints are reliable evidence of the presence of man. The paper is founded mainly on the series of specimens brought together in the Sedgwick Museum at Cambridge. The following paragraph deserves serious consideration nowadays: ‘‘ Let us now take a few groups of naturally shaped flints. First there are those which are called ‘Figure Forms’. M. Boucher de Perthes was the first to call serious attention to them. He was the man who in 1857 announced the discovery of palzeolithic implements in the valley of the Somme; and it is often said in reply to those who criticise adversely the evidence upon which a more remote antiquity is now claimed for man than had been previously supposed, that, the same thing was done in the case of Boucher de Perthes’ discoveries. But the rejoinder is obvious. Had Boucher de Perthes not supported a correct theory by bad evidence the acceptance of his views would not have been so long retarded. We cannot in science give a bill of indemnity for false reasoning, though it was in support of a suggestion which after- wards turned out to be true.” Dr. Holst in the second paper gives a short and very clear account of the prehistoric flint-mines near Malmo in Southern Sweden. These pits are sunk in gigantic erratic blocks of chalk, the largest being about 3000 x 1500 x 10-20 feet. Though necessarily much smaller, on account of the shattered state of the anal these shafts are comparable to those of Grimes Graves, which they resemble in having been hewn out with stag’s horn picks. The implements and scrap from the sites, however, do not closely resemble those from the English locality, and seem to show that these mines were worked from the later part of the Neolithic to the Early Iron age. The third work under review is an excellent piece of archeological survey, detailing the camps and graveyards, the rock-shelters and trails of the Red Indians in certain parts of New Jersey. It consists of a mass of facts well illustrated by maps, plans of rock-shelters, and photographs of pottery, of great local interest, but impossible of review. It is, however, an illustration of the interest which citizens 1 Professor T. McKenny Hughes, ‘‘ Flints’’?: Cambridge Ant. Soc. Coll., vol. xvili. . Dr. N. O. Holst, ‘‘ The Swedish Flint Mines’’: Report on the Excavations at Grimes Graves, 1914. M. Schrabisch, ‘‘ Indian Habitations in Sussex County, New Jersey ’’; and L. Spier, ‘‘Indian Remains near Plainfield, Union Co., and along the Delaware Valley ’’: Geol. Surv. New Jersey, Bull. 13, 1915. N. H. Winchell, ‘‘ The Weathering of Aboriginal Stone Artifacts. No. 1. A consideration of the Palsoliths of Kansas’’: Collections of the Minnesota Historical Society, vol. xvi, pt. i. Reviews—O. P. Hay—Mammals of Iowa. 35 of the United States feel in the history of their country, and the thoroughness with which they are recording the fast vanishing remains of the splendid savages whose place they have taken. The last archeological work which it falls to me to review claims to deal with the Paleoliths of Kansas. The author divides up a series of implements into four groups, two said to be of Paleolithic age, the others later and early Neolithic. He correlates them with the many glaciations of North America. All these specimens seem to be surface finds. None were found with extinct animals or in relation to glacial deposits. The whole scheme rests entirely on depth of patination and on certain implements which are said to be rechipped. Some of the implements photographed do resemble genuine paleoliths in shape, but others are as obviously allied to modern Indian work. The whole book is a somewhat pathetic example of misapplied energy. There is not the slightest evidence that any one of the American implements described was made during the Ice Age or before it. So far as I know, only one implement has been found in America that has any claim at all to be considered a palzo- lith, the arrowhead found by Professor Williston in association with an extinct bison; and this is of a relatively modern Indian type. II1.—Tue Puristocent Mammats or Iowa. By O. P. Hay.’ oe paper consists of 499 pages of text and 75 plates, mostly from i photographs. It begins with avery valuable account of the main facts of the glacial geology of Lowa, describing the distribution of the tills laid down during five glacial stages and of the deposits associated with the interglacial intervals. This section is provided with an elaborate bibliography. The second part of the paper gives in as untechnical a way as possible, descriptions of the animals found in the Pleistocene of this State, together with some that will no doubt be found in the future. ‘These descriptions are founded on Iowan specimens, but when these are incomplete others are figured and their measurements given. The whole forms a very valuable work of reference, full of clearly arranged facts, but does not seem to contain any general conclusions as to the relations of the many animals discussed to the divisions of Pleistocene time ; in fact, the existing collections seem to be still too small to yield much in the way of wide generalizations. TV¥.—Txe Coat-mMEasuRE AMPHIBIA AND THE Crossopreryera. By R. L. Mooprs.? N this short paper Dr. Moodie gives a phyletic tree of the vertebrates, of interest as representing the views of a student with great knowledge of the smaller Coal-measure amphibia, still unfortunately so very incompletely known. He then gives a short summary of the geological history of the amphibia, which is slightly 1 Towa Geological Survey, vol. xxiii, 1914. 2 The American Naturalist, vol. xlix, p. 637. 36 _Revrews—The Trilobite Harpes. incomplete in not Sea the amphibia from the Mississippian of Scotland and the frog from the lithographic slate of Portugal. A comparative table shows that in many features the Crpeas: pterygian fish and the amphibia approach one another. Finally, the high degree of specialization and complete adaptation to nearly all conditions of vertebrate existence of the Coal-measure amphibia is insisted upon. V.—New Yorx Strate Museum. Patzxozorc Fisuus, Erc. ESTORATIONS of Bothriolepis and Cephalaspis as restored by Patten and modelled by Marchand are figured as among the new items on exhibition in New York. The State mining exhibit at the Panama-—Pacific Exposition is described, and a report is given on the preservation of natural monuments. These latter, now added to the former trusts, are the Lester Park (or the “‘ Oryptozoon Ledge’’), Stark’s Knob, a dome-shaped volcanic knoll, the Clark reservation (a glacial park), Logan Park (where W. E. Logan began his official work) with its vertical ledge of Ordovician or Cambrian limestone-conglomerate, and the Hugh Miller Cliffs, Scaumenac Bay, celebrated for their Old Red fishes. All these places are briefly described in the Museum Bulletin 177 of the New York State Museum, 1915. This Bulletin also contains, we believe for the first time, an excellent attempt at depicting a ecological section by colour photography. ‘There is a short paper by Hudson on Porocrinus; others by Clarke on American Devonian, the Oriskany, and the Rifted-Relict-Mountain ; and by Miller on Trenton Contortions and the Rift on Chimney Mountain. Among accessions we note the Silas Young minerals. ViI.—Srrucrurt or tHE Tritosire A ARPzS. N preparation for a monograph on the trilobite Harpes, Dr. Rudolf Richter has studied the structure by means of thin sections, and _ has presented an outline of his main results in Zoologischer Anzerger , (vol. xlv, pp. 146-52, Dec. 1914). He finds that’ the pits on the brim (French ‘limbe’, mistranslated as ‘limb’ by several English writers) are not blind, as stated in text-books, but pierce right through. Precisely the same structure extends over a considerable tract “of the swollen part of the head-shield. All this perforate extension is composed of two distinct layers (outer and inner) of chitinous integument. From the inner boundary of the inner layer a thin ventral membrane extends below the true head cavity. ‘he marginal suture (on the outer edge of the brim) has been regarded as the ocular suture, and the under fold of integument as the free cheeks; and on this view depended Beecher’s conception of the Hypoparia. A corollary of that view was that the eyes on the upper surface could not be homologous with the true eyes of other trilobites. Richter, however, shows that the microscopic structure is quite opposed to that forced hypothesis. The eyes are true eyes, and though the ocular suture is obscured the free cheeks occupy the nano position. The marginal suture is, in his opinion, a special Reviews—Edriouasteroidea. oF development to permit the separation of the under layers of integu- ment in course of moulting, and traces of this division between the two layers, though sought in vain by some previous writers, have been found by him on the sides of the perforations. Consequently Harpes, Trinucleus, Dionide, and the rest, though highly specialized, are not essentially different from other trilobites, a view which accords with that expressed by Professor Swinnerton in the Groroercat Macazine for November, 1915. Dr. Richter also elucidates the peculiar method of rolling up the carapace, and believes that the backwardly directed horns of the head-shield served, not as ‘mud-shoes’, but as balancers when the animal swam; a similar balancer- function has been ascribed to the horns of Ceratocystis, Cothurnocystis, and Dendrocystis (see Grot. Mac., Sept. 19138, plate xii). VII.—Srvupms rn EprroasreromEa, I-IX. By F.A. Barner, M.A., D.Se., F.R.S., etc. 8vo; pp. 136, with 13 plates. Published by the author at ‘‘ Fabo”’, Marryat Road, Wimbledon, London, 8. W. 1915. Price 10s. 6d. Jae highly, important work, completed in the past year, was begun as a series of articles in the Grotocican MaeazinE in 1898 and continued, with intervals, until 1915, extending over seventeen years. In the reprinted form there will be found some valuable additions, and the very numerous illustrations in the text, as well as the thirteen beautiful plates, are all reproduced with care. To any student desirous to become acquainted with the morphology and classification of the Echinoderma the present work must form an essential part of his library; and as the original ‘‘Studies’’ are scattered through the volumes of the GrotocicaL Magazine during so many years, we must all feel extremely grateful for the ‘‘ Author’s Edition ’’, as Dr. Bather calls this volume. We heartily congratulate the author upon his completed work, and wish him many more years in which to continue his difficult but ‘delightful studies of other sections of the Echinoderma. Vill.—Caratogure or Types anp Ficurep SprcIMENS oF BritIsH CRETACEOUS LAMELLIBRANCHIATA PRESERVED IN THE MUSEUM OF Pracrican Gxzotocy, Lonpon. Summary of Progress of the Geological Survey for 1914, Appendix II, pp. 66-79, 1915. R. H. A. ALLEN, F.G.S., one of the Paleontologists of the Geological Survey, is the compiler of this very excellent and nseful work. It forms the eighth of a series of similar lists which have been issued under the same auspices, the previous subjects treated being Eocene and Oligocene (1900); Pliocene, Pleistocene, and Devonian (1901); Phyllocarida and Paleozoic Echinodermata (1902); Rhetic, Lias, and Inferior Oolite Gasteropoda (1908) ; Great Oolite, Cornbrash, and Corallian Gasteropoda (1904); Rheetic and Lias Lamellibranchiata (1905); Lower, Middle, and Upper Oolite Lamellibranchiata (1906). These catalogues are all modelled on the same plan, the genus and species of each entry standing out clearly in a bold black type, followed by the author’s name, beneath 38 Reviews—Prof. J. Barrell—Isostasy. being the reference in literature where the description and figures are to be found, and afterwards are given the geological horizon, locality, and registration number. A valuable addition, we think, might have been introduced in connexion with the geological information offered, that of Continental equivalents, as for instance, when quoting the horizon of the Atherfield Beds as ‘ Lower Green- sand’ the term ‘ Barremian’ might have been given in brackets. A modification of this kind would have been most welcome to the foreign student of geology in enabling him at once to understand the value of a purely English term and its exact significance in the Cretaceous Series. It is interesting to mention that this catalogue differs from all the former, as it includes a number of type or figured specimens that were originally in the Museum of the Geo- logical Society of London, these being indicated by the letters G.S. EN. IX.—Isosrasy, AND THE ASTHENOSPHERE. Tur Srreneru or tHE Earrn’s Crust. By Josnpa Barrett. Journal of Geology, vol. xxii, pp. 28, 145, 209, 289, 441, 537, 655, and 729, 1914; vol. xxiii, pp. 27, 424, and 499, 1915. N this remarkable series of papers, which is worthy of the most careful study, Professor Barrell discusses the problems arising from the existence, now well established, of isostasy. He shows from geodetic data and from geological evidence (e.g. the building up of extensive deltas) that ‘‘isostasy . . . is nearly perfect, is very imperfect, or even non-existent according to the size and relief of the area considered”. The close degree of isostatic equilibrium postulated by Hayford is not admitted, but since over large areas equilibrium is maintained in spite of denudation, deposition, and mountain- building, it follows that there must be some counter movement taking place within the earth. To explain the mechanism of isostatic compensation Barrell introduces the conception of an asthenosphere— a sphere of weakness—which, as he clearly shows, must be below the level of compensation, and of great thickness. The excess pressure of heavy columns of the lithosphere is transmitted to the asthenosphere, within which the lateral movements of restoration take place. In proof of the existence of some such zone of weakness the author indicates the impossibility of widespread flowage in the zone of compensation; he shows that below the level of compensation the earth is unable to withstand the stresses thrown upon it by the greater undulations of topographic relief; and finally he cites Schweydar’s conclusion, based on measurements of earth tides, that there seems to exist a yielding layer 600 kilometres in thickness below the 120 kilometres of the lithosphere. It is suggested that recrystallization is the chief factor determining weakness, plasticity, and flowage. It should be remembered that effective plasticity, signifying a low elastic limit, is by no means incompatible with a high rigidity. The flowage of glaciers is an instructive case in point. Recrystallization will clearly be favoured by high temperature conditions. This leads to another line of Reviews—Delta Deposits of the Nile. 39 argument supporting the existence of the asthenosphere, for the distribution of the radio-elements in the earth’s crust carries with it the deduction that fusion temperatures (under high pressures) can only be approached far below the level of compensation, probably 200 km., or more, below. In keeping with this view, Barrell holds on mechanical grounds that the source of igneous activity is well within the asthenosphere. Recrystallization, culminating in local fusion, is brought about by the gradual contact of the temperature curve with the fusion-solution curve, and ‘‘if this is the cause of the disappearance of strength, it should be as much as 300 km. deep and extend through some hundreds of kilometres”’. The author draws a short sketch of the initiation of magmas and their ascent into the crust. He supposes that they are of basaltic or andesitic composition, though in the opinion of the present writer the possibility of the rocks at such depths being wholly of ultra-basic composition is worthy of consideration, together with the mechanism of igneous intrusion implied by that view. Professor Barrell’s papers constitute a valuable and imme contribution to terrestrial dynamics, only the fringe of which has been touched upon in this brief and therefore inadequate review. ArtHur Homes. X.—Detra Duposrrs or tHe Nite. Tae Suzsor. or Carro. By E. C. Bowpen Surrg. Cairo Sci. Journ., Nos. 97 and 98, vol. viii, pp. 289-50, with 3 plates, 1914. NE of the most interesting problems connected with the delta deposits of the Nile is their evidence on the supposed isostatic movements of the area; and Mr. Bowden Smith discusses the evidence of many bores under the Nile delta upon the supposed subsidence. He quotes Professor Watts to the effect that the old soils, one below another, prove conclusively the repeated subsidence of the delta, and he remarks that according to other authorities the ‘low-level deposits at least were laid down beneath the sea when it extended southward up the Nile Valley. Mr. Smith states that the delta is not composed of an endless succession of interlaced deposits of sand and clay; he concludes from the nature of the deep-level deposits and their irregular distribution there is reason to believe that they were formed by river-action working under conditions similar to those that prevail on the surface at the present day. The author remarks that the evidence on this question is not conclusive, and that some of the deep-level material may be marine, but he holds that repeated substances have taken place between long intervals of rest. JWG: XI.—Doetrer’s Hanpsoox or Mrneratoay.—We recently received the fourth part (Dresden and Leipzig: Theodor Steinkopff. Price 6.50 marks) of the third volume of the comprehensive Handbuch der Mineralchemie, edited by Professor C. Doelter, which was issued in July, 1914, just before the outbreak of War. It forms the penultimate part of the volume, and in its 160 pages deals with the 40 Reviews—Russian Meteorite. concluding species among the phosphates and with the greater number - of arsenic compounds. A conspicuous feature of the work consists of the ample discussion of chemical methods which are introductory to the descriptions of the principal mineral groups; thus, in the present part we find an able article from the pen of Professor Dittrich on the analysis of the arsenates. The descriptions of the several species seems on the whole complete and up to date. We have under turquoise a good account of Schaller’s recent work on the specimens found in Virginia, which cleared up the mystery of the crystallization of that species and showed it to be isomorphous with chalcosiderite. Following the chapters on monazite and xenotime comes an interesting one on the commercial use of the so-called rare earths. We have noticed one important omission. In the section on tilasite, the calcium-magnesium arsenate, no reference is made to the memoir published by Prior & Smith in the Mineralogical Magazine in 1911 on the crystals found by Ferrar in the manganese-ore deposits of Central India. In consequence the crystallographical particulars of the mineral are reduced to the single—erroneous—sentence: ‘‘Kristallisiert vielleicht triklin”; the crystals, however, actually belong to the clinohedral class of the monoclinic system. XIJ.—Russtaw Merrorrre.—In the Proceedings of the U.S. National Museum (vol. xlix, pp. 109-12, with plate xxxvii) Mr. George P. Merrill briefly describes the meteoric stone which fell at Indarch in Russia on April 7, or possibly April 9, 1891. It is a dark greenish-grey in colour, firm and compact in texture, and thickly studded with small, dark-green chondrules and nodular masses of metal and troilite, rarely more than 1 mm. in diameter. Graphite is very prevalent. Oldhamite, calcium sulphide, occurs sometimes interstitial and sometimes enclosed in enstatite; it is yellow-brown, sometimes greenish, in colour, and completely isotropic. The presence of carbonic acid in the analysis suggested breunnerite, but the actual occurrence could not be determined. The stone is a carbonaceous chondrite (Ke). XIII.—Brisr Noricers. 1. QurnevenniAL Review oF tHE Minera Propuction oF Inpra. By Sir T. H. Hortanp and Dr. L. L. Fermor. Revised for the years 1909 to 1918 by Dr. H. H. Haypen and Dr. L. L. Frrmor. Records Geological Survey of India, vol. xlvi, 1915. This valuable report contains a great deal of useful information regarding the occurrence of economic minerals in India. Listed according to their values the eight principal minerals are coal (£3,800,000 in 1913), gold, petroleum, manganese ore (about 40 per cent of the world’s production, and exceeded only by Russia), salt and saltpetre, mica (65 per cent of world’s production), and lead ores. During the period under review the tin and wolfram industries in Lower Burma have made considerable strides, while rubies and other precious stones have suffered some depression. The Reports & Proceedings—Geological Society of Glasgow. 41 production of monazite from the seashore of Travancore marks the commencement of a new mineral industry. 2. On tHe Porosity or tHE Rocks or THE Karroo System In Sourn Arrica. By A. L. pu Torr. Trans. Roy. Soc. S. Africa, vol. iv, pt. 111, pp. 169-80, 1915. The rocks of the Karroo system cover fully one-half of the Union of South Africa, and have sometimes been considered capable of furnishing important supplies of artesian water. The author has made a large number of measurements of porosity and specific gravity on fresh specimens from various horizons of the formations represented. His results show that the porosity of these rocks is low, and that, except where fissures and joints increase the capacity for water storage, strong supplies cannot be anticipated. 3. BrieHron’s Lost River.—Mr. K. A. Martin has contributed to the Transactions of the South-Eastern Union of Scientific Societies, 1915, a very complete account of the Wellesbourne, a stream which rose near the upper end of Patcham Street and entered the sea at the Pool, Pool Valley, Brighton. Its operations are now confined by a sewer, but in former days it seems to have been the cause of frequent flooding and other trouble to the town. REPORTS AND PROCHHDINGS. ee ——————. I.—GerotoctcaL Society or GLascow. At a meeting of the above Society held on November 11, the office-bearers for the session were elected. ‘Mr. Alexander Scott, M.A., B.Sc., read a paper on “ Primary Analcite and Analcitation”. He discussed the occurrence and form of analcite in igneous rocks and reviewed the opinions of various authorities concerning it. British and American petrologists generally favour the opinion that the mineral is primary, while Continental investigators hold the view that it is secondary. The chief evidence in favour of the latter theory is the altered condition of associated minerals, but this can be shown to be due to reactions between the analcite and minerals previously formed; thus felspar is replaced by analeite, augite has a rim of soda-pyroxene, and olivine and magnetite are surrounded by biotite. These undoubtedly arise by the corrosion of the early minerals by a magmatic residuum rich in water and soda. The general conclusion is that analcite is primary in many rocks, particularly in the great Permo-Carboniferous suite of the West of Scotland described by Tyrrell. Professor Gregory complimented the author on his paper, and said it was satisfactory to find that, while there was ground for the views of both the British and the Continental workers, the balance of truth lay with the British. Mr. G. W. Tyrrell said that in addition to the evidence brought forward by Mr. Scott, the fact that analcite is such an important constituent (sometimes about 40 per cent) of many rocks points to its being a primary ingredient, as such rocks, minus their analcite, 42 Reports & Proceedings—Geological Society of London. would be too spongy in structure to resist the pressures to which they had undoubtedly been subjected. He also compared its mode of occurrence with that of quartz in a granite, and thought that the two were quite analogous. Mr. Peter Macnair, F.R.S.E., F.G.S., read a paper on ‘‘ The Horizons of the Type-specimens of Dithyrocaris tricornis and D. testudinea’”’. He detailed what was known as to the discovery of these interesting fossils, and pointed out that, while the facts connected with the East Kilbride occurrences were well ascertained, there was confusion with regard to the exact locality from which the Paisley specimens came and their horizon was not known. He stated that he had recently found specimens in an old dyke and an old house built of a peculiar limestone near Arklestone, Paisley, and showed that this material must have come from certain old quarries, now obliterated, and that these quarries must have been opened in the Blackbyre Limestone. Mr. R. G. Carruthers, H.M. Geological Survey, said that he quite agreed that these specimens must have come from a peculiar bed lying at the top of the Blackbyre Limestone at Arklestone, and congratulated Mr. Macnair on having settled a question that had been for so long a source of discussion. I1.—Grotoeicat Soctery or Lonpon. 1. November 17, 1915.—Dr. A. Smith Woodward, F.R.S., President, in the Chair. Mr. John Parkinson gave an account (illustrated by specimens and lantern-slides) of the Structure of the Northern Frontier District and Jubaland Provinces of the East Africa Protectorate, made by him while conducting a water-supply survey for the Government of the Protectorate. A floor of gneisses and schists, among which the Turoka Series of metamorphosed sediments was found at several places, is overlain on the western side by lavas, including those arising from the volcanoes Kulal, Assi (‘Esie’ of the maps), Hurri, Marsabit, etc., and by probably older lava-fields, which together extend as far'as long. 39° E. On the south, it was found that the lavas north of Kenya reached the Guaso Nyiro, leaving ‘inselberge’ of the crystalline rocks in their midst, but that a high gneiss country extended north-westwards from lat. 1° N. and long. 38° E. to within a short distance of Lake Rudolf. Eastwards the Coastal Belt of sediments proved to be of Upper Oxfordian age and to extend to long. 403° KE. (west of Hil Wak), and these were lost southwards under the great alluvial plain of Jubaland. At intervals throughout the alluvial plain ard lying in hollows in the Jurassic rocks, disconnected exposures were found of soft calcareous sandstones or limestones (Wajhir, Eil Wak), the age of which cannot now be definitely fixed. Evidences of the desiccation of the country were, it was thought, shown (1) by the Laks or. water-channels characteristic of Jubaland, which contained surface-water only during the rainy season and then Reports & Proceedings—Geological Society of London. 43 extremely rarely, if ever, throughout their length; (2) by the presence of freshwater molluscs in the scarcely consolidated beds of such Laks and at other places where now no surface-water is present (Buna and near the Abyssinian frontier); and (3) by the presence of wells along fault-lines and in other places where, but for the previous presence of springs, it appears improbable that the natives would have begun sinking. The region between Lake Rudolf and Marsabit was pointed out as one of exceptional interest, which the speaker had so far not been able to investigate. The depression between the Mathews and associated ranges and the Abyssinian frontier on which the Marsabit and Hurri volcanoes were situated, and the origin of the Kuroli Desert (Elgess), were the outstanding features of the district that required further elucidation. Mr. G. C. Crick stated that the Cephalopoda submitted to him by Mr. Parkinson consisted chiefly of crushed ammonites from dark-grey shales at Kukatta on the Juba River (lat. 2° 8’ N.), there being also a belemnite preserved in a yellowish-brown rock-fragment from Serenli on the same river and somewhat north of Kukatta. He concluded that the shales at Kukatta were of Upper Oxfordian (Sequanian) age. Mr. R. Bullen Newton had examined a small series of non-marine »Kainozoic molluscan remains belonging to recent species, and associated with hard and soft limestones, calcareous sandstones, and conglomerates, which had been collected by Mr. Parkinson, and had determined about nine genera and twelve species. No vertebrates - occurred with these shells, hence their age would probably be younger than the Omo-River deposits north of Lake Rudolf, and that yielded a somewhat similar molluscan fauna, but with the addition of Dinotherium and other vertebrate remains. The presence of that genus, as pointed out by Dr. Haug (Zraité de Géologie, 1908-11, vol. ii, p. 1727), was indicative of the Pontian or Upper Miocene Period. There are, however, some lacustrine beds near Lake Assal, in French Somaliland (formerly regarded as Abyssinia), which contain shells also bearing a resemblance to those collected by Mr. Parkinson in British East Africa, especially MMelania tuberculata, Cleopatra bulimoides, Corbicula fluminalis, and C. radiata, which are common to both sets of deposits. These Lake Assal beds, which are also without vertebrate remains, have been identified by Aubrey (Bull. Soc. Géol. France, ser. 11, vol. xiv, pp. 206-9, 1885), and Pantanelli (Atti Soc. Toscana Sci. Nat. Proc.-verb., vol. v, pp. 204-6, 1887, and ibid. vol. vi, p. 169, 1888) as of Pliocene age. If, from these facts, such widely distant beds can be recognized as contemporaneous, then the suggestion may be made that the northern half of British East Africa was probably an extensive freshwater region during Pliocene times, limited on the north by Lake Assal, on the east by Suddidima, on the south by Archer’s Post and the Mount Kenya plateau, and on the west by Lakes Rudolf, Stefanie, and Marguerite. Assistance in the determination of these shells had been kindly rendered by Mr. E. A. Smith, 1.8.0. +4 Reports & Proceedings—Mineralogical Society. 2. December 1, 1915.—Dr. A. Smith Woodward, F.R.S., President, in the Chair. The President exhibited lantern-slides lent by Professor Elliot Smith to illustrate the fossil human skull found at Talgai, Darling Downs, Queensland, in 1914. The specimen was brought to the notice of the British Association in Sydney by Professor T. W. Edgeworth David, and would shortly be described by him and Professor Arthur Smith. It was obtained from a river-deposit in which remains of Diprotodon and other extinct marsupials had already been discovered, and there could be no doubt that it belonged to the Pleistocene fauna. It therefore explained the occurrence of the dingo with the extinct marsupials. The skull is typically human and of the primitive Australian type, but differs from all such skulls hitherto found in possessing relatively large canine teeth, which interlock like those of an ape. The upper canine shows a large facet worn to its base by the lower premolar. The discovery of the Talgai skull is, therefore, an interesting sequel to that of Mr. Charles Dawson’s Piltdown skull, in which the canine teeth are even more ape-like. Dr. J. W. Evans discussed the different methods of obtaining the directions-image (‘‘interference figures’’) of a small mineral in © a rock-slice, unaffected by the light from neighbouring minerals. He preferred the use of a diaphragm in the focus of the eye-piece, in conjunction with a Becke lens. He also described the inferences that might be drawn from the ~ form, position, and movement on the rotation of the stage of the isogyres (dark bars or bushes) in the directions-images, both of chance sections and those cut parallel to planes of optical symmetry or at right angles to optical axes. He showed how the character or sien of the crystal and its approximate optic axial angle might be determined. IIT.—Mineratoeicat Sociery. Anniversary Meeting, Movember 9, 1915. W. Barlow, F.R.S., President, in the Chair. W. Barlow: Crystallographic relations of allied substances traced by means of the law of valency volume. ‘The ordinary parameters of a crystal do not necessarily express the actual ratio between the minimum translations of the crystal structure, and it is justifiable to multiply one or sometimes two of them by a small integer in order to obtain the equivalence parameters. A number of cases were taken which showed that in crystals which either contain the same radicle or closely related radicles the similar parts are arranged in identical strata intercalated between the remaining constituents of the crystal. A. F. Hallimond: On Torbernite. From measurements made on several specimens the axial ratio a: ¢ = 1: 2'947 was determined, and the forms 001, 101, 108, 111, 112, besides vicinal faces, were observed. The mineral becomes unstable at vapour-pressures about one-third that of water, and passes into Rinne’s meta-torbernite I. At higher temperatures the transition-curve rises sharply, and meets the vapour-pressure curve of water at 75° C., above which torbernite has no stable existence in air. T. V. Barker: On the solution Correspondence—Bernard Smith. 45 of the problem of Four Tautozonal Poles. The indices of two poles C, D may be expressed as functions of those of the two other A (adc), B (def) in the form (pa+qd, pb+-ge, pe+ qf), (ma+nd,mb+-ne, me+nf) where p, g, m, m are small positive or negative integers. Since npcot A D=(np-mq)cotAB+mqcot AC, a table of natural cotangents enables a numerical example to be solved rapidly. Usually p=q=1, and the equation reduces to ncotAD=(n-m)cotAB-+ mcot AC. L. J. Spencer: Crystals of Iron Phosphide (Rhabdite) from a Blast- furnace. The small, acicular, tin-white, and strongly magnetic erystals were found sparingly in cavities in a large mass of metal at the bottom of a blast-furnace near Middlesbrough. They are tetragonal (sphenoidal -hemihedral) with the axial ratio, -@:c=1:0°3469. Dr. G. T. Prior: The Meteoric Stone of Cronstad Orange Free State. At the above meeting the following officers and members of Council were elected: President, W. Barlow, F.R.S.; Vice-Presidents, Professor H. L. Bowman and A. Hutchinson; Treasurer, Sir William P. Beale, Bart., K.C., M.P.; General Secretary, Dr. G. T. Prior, F.R.S.; Foreign Secretary, Professor W. W.- Watts, F.R.S.; Editor of the Journal, L. J. Spencer; Ordinary Members of Council, Dr. J. J. Harris Teall, F.R.S., F. N. Ashcroft, Professor H. Hilton, Arthur Russeli, W. Campbell Smith, Dr. J. W. Evans, Dr. F. H. Hatch, J. A. Howe, T. VY. Barker, G. Barrow, Dr. C. G. Cullis, and F. P. Mennell. CORRESPON DHNC#. ‘ON CERTAIN CHANNELS.” Srr,—A section of Professor Bonney’s recent essay On certain Channels attributed to overflow streams from ice-dammed lakes! is devoted to an extremely courteous criticism, but final rejection, of _ my interpretation of glacial phenomena in the Black Combe area.’ Since he advances an alternative hypothesis to account for the above- mentioned channels, [ am sure he will pardon me if I, in my turn, offer a few critical remarks. I must first protest against Professor Bonney’s assumption (vede title of his paper) that I ascribe practically all these channels to overflow waters from ice-dammed lakes. In many cases, as I clearly state, they were merely carriers of the normal marginal drainage of an ice-sheet. Nor do I invent ice-dams ‘‘almost by the dozen’’. As regards overflows from lakes, one dam—the Irish Sea Ice—is quite sufficient. In my description the drainage channels are discussed and ' interpreted in the light of observations, recorded on 6 in. field maps, and fall into place as an important chapter in the glacial history of the area. Professor Bonney states that he accepts most of my facts, but differs from my conclusions; yet, having made this admission, and agreeing that land*ice ‘‘occupied all this district during some part of the Ice Age’’, he appears to ignore the evidence 1 Published by Bowes & eae Cambridge, 1915. 2 Q.J.G.S., vol. Ixviii, 1912. 46 Correspondence—Bernard Smith. relating to the composition, character, and location of the glacial drifts, as well as that furnished by erratics, ice-moulded surfaces, and strie. Having thus divorced these anomalous channels from their surroundings, he has constructed a theory to explain their origin (as it seems to me) based chiefly upon their shape and rate of fall. If land-ice ‘‘ occupied all this district during some part of the Ice Age’’, and there was no Irish Sea Ice, I venture to ask why (as its markings show) the ice from Eskdale first turned south, along the seaward slope of Black Combe, and then swung to the east and north- east into the mouth of the Duddon estuary; and why the Whicham Valley Ice, moving first in a south-westerly direction, was also directed towards the south-east and east near the mouth of that valley? Why did it not ride out to sea? What was the impelling force that turned it aside ? Professor Bonney doubts whether marginal streams could cut channels in granite in a short time. He may read of recent examples described by Von Engeln,' to whose article I have already made reference. My critic admits that the systems of parallel trenches on the west coast, as contrasted with the preglacial drainage, are abnormal in direction, and finds some difficulty in explaining this anomaly, but confesses himself happier when dealing with the channels east of Black Combe, where ‘‘the trenches take a more normal course’’. The explanation issimple: in the first case the trenches were marginal to the Irish Sea Ice, and are therefore transverse to the normal drainage, whereas in the second case they were marginal to the local | Lake District glaciers which occupied the present drainage lines at a late stage of the glaciation. If, as Professor Bonney maintains, the dry channels on the west coast are preglacial, how does he explain the presence of thick glacial drift upon the ground between them, and upon the higher inland slopes, but not within them ? Perhaps the weakest part of this new hypothesis is an attempt to explain the ‘in-and-out’ channels by marine erosion of the seaward wall. A preglacial submergence cannot be invoked, because one of the long ‘in-and-out’ channels (Monk Foss) is cut entirely in glacial drift; nor can we admit a postglacial submergence, for that would have entirely destroyed the typically hummocky character of the drift on the plain between Millom and the mouth of the Esk. Moreover, even were ‘in-and-out’ channels at this spot due to marine erosion, we cannot explain in this manner the ‘ in-and-out’ channels of other districts far from the sea. Finally, one might pertinently ask how pre-Triassic valleys could have maintained such sharp well-defined contours to this day. As a field-geologist I have frequently noticed the “‘ half effaced features of an earlier topography ’’, but in few instances have I seen anything more blatantly modern in appearance than these marginal or overflow- channels in the Black Combe district, or, indeed, in North Wales, where they are cut in fairly soft shales. 1 “Phenomena associated with Glacial Drainage and Wastage’’: Zeit. Gletscherkunde, vol. vi, pp. 126-31, 1911. Correspondence—Prof. T. G. Bonney. 47 This conception of old drainage systems running parallel to the contours of the mainland, in Cumberland, Haddingtonshire, S.E. Ireland, Denbighshire, Flintshire, etc., when coupled with the warping movements necessary to explain the steep fall of the channels, sets the mind, no less than the land, awhizrl. BERNARD SMITH. THE GEOLOGICAL AGE OF THE CARRARA MARBLES. Sir,— Permit me to comment briefly on Dr. Du Riche Preller’s paper on the Carrara Marble District.1 It contains a quantity of interesting information, topographic and economic, but does little, in my opinion, to settle the question as to the age of those rocks or strengthen the position of the Italian geologists. I had their map with me in the autumn of 1889, and in regard to faults (which Dr. Preller considers to be almost negligible) wrote thus in my diary: ‘‘ In order to accept the geological succession they have indicated, we must explain the proximity of ordinary dark mechanically disturbed limestone (just like some of that at Spezzia) with lighter varieties to perfectly typical Carrara marble.” I was aware that the statuary marble is intercalated with marbles of inferior quality, but instead of finding any sign that the metamorphism was a result of pressure, maintain that, as shown by the microscope, that marble has escaped (as I stated) from the crushing which has affected its associates. As to ‘metamorphism’ and its effect on sedimentary rocks, I have been doing my best to study the whole question since about 1875, have spent much time and money in examining alleged passages from crystalline schists to comparatively unaltered sediments or intercalations of the two, with the invariable result that the evidence was never conclusive and very commonly worthless; in fact, I have not been able to discover any case (I have not restricted myself to the Alps) where a truly crystalline limestone, such as that of Carrara, is in stratigraphical sequence with a sedimentary rock to which a date ‘can be assigned on the evidence of fossils, except in the case of contact metamorphism, which, so far as I am aware, is not exhibited in the Apuan Alps. Dr. Preller’s paper contains no evidence that he has made use of the microscope in studying these Carrara rocks, and as I know the vague use of the term ‘schist’ by many Continental and some British geologists I am unable to discuss his sections (Figs. I-LV) beyond saying that only one of them seems to demand an explanation, and this I think my past experience would enable me to supply. T. G. Bonney. RENE ZEILLER—MASTER PALHOBOTANIST. Sir,—In the current number of ature there is a short tribute by Professor Seward to Professor Zeiller, whose death this week in Paris we all deplore. I should like to add a word in token of the deep and lasting affection and reverence the great Palzobotanist inspired in his younger colleagues in many countries. *1 Grou. MAG., December, 1915, pp. 554-65. 48 Ohituary—Arthur Vaughan. Long before I had personally met him, his work, so deep, so wide, so balanced, so exceptionally thorough, had proclaimed him to me as the master paleobotanist of our time. Professor Seward has referred to his magnificent memoir on the fossil flora of Tonkin: it is, I think, the most perfect piece of paleobotanical work extant—the most perfect in not only containing conclusions of far-reaching and profound significance, but in being the freest from the minor defects of misapprehensions, ‘of carelessnesses, misquotations, and incomplete or incorrect references which are present in nearly all work and abound in some. It was on visiting Professor Zeiller in Paris, however, that the full extent of his work became apparent tome. The wonderful collection of fossil plants which he had brought together and so intimately knew is, in some respects, unsurpassed and is invaluable to students. Then, too, Professor Zeiller held a unique position in relation to practical mining, and was the guide, philosopher, and friend of Government Departments and coal-miners in a way which is almost unimaginable in this country, where palzobotanists are held in little honour and are put to little practical use. His prescience, based on detailed paleeobotanical knowledge, saved his country many tens of thousands of pounds. But surpassingly in Paris did the enchanting personality of the great man become apparent. Unique were his cenerosity, his sincerity, his aristocratic and beautiful courtesy and heipfulness towards the younger workers, at whose service he placed the whole storehouse of his profound and well-balanced knowledge. Even in Berlin, where I have heard nearly every other paleobotanist roundly abused, Zeiller —Frenchman though he was—was spoken of with affection and respect. It is due only to the fact that Professor Zeiller worked in the -* Cinderella’ science. of paleobotany instead of in some popular and widely respected science like chemistry that his death is not universally hailed by the general public as the irreparable loss it is. To us who knew and loved him, as to his colleagues all over the world, no one can replace René Zeiller. Marte C. Sores, Lecturer in Palzeobotany, University College, Roden 14 WELL WALK, HAMPSTEAD HEATH, N.W. December 10, 1915. (SpSneAGoyya IS, N ee ARTHUR VAUGHAN, M.A., D.Sc., F.G.S., Lecrurer In GEroLocy oF THE University or OxrorD. We regret to record the death of Dr. Arthur Vaughan, which occurred on Friday, December 8, 1915, at 315 Woodstock Road, Oxford, in his 47th year. We hope to give a notice of his geological work in the next number of the Magazine. LIST OF BOOKS OFFERED FOR SALE AT THE NET PRICES AFFIXED BY DULAU & CO., LTD., 37 SOHO SQUARE, LONDON, W. CHAPMAN (F.). 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(PlateII.) .. .. 49 | Stegocephalia of Senekal, O.F.S. i By Dr. EH. C. N. van Hoepen ... 83 The Punctation of Terebratulid J. ; s Shells. By F. G. Purctvat, ae Economic ee Canada 87 “B.Se., F.G.S. (Plate III atid sostasy and Radioactivity. By 2 Text-figures.) ... ii eRe ESO 1 G. F. Becker... 88 iy Besse oe ‘ | The Klondike and Macon Goldfield 89 er The Fluvio-glacial Gravels of the The Mineral Resources of the ' Thames Valley. By R. M. Philippines LOU i ee os 89 DEELEY, M.Inst.C.H., F.G.S. Lavas of Hawaii. By W. Cross... 89 (Plate Bes. 57 | Wabana Iron Ore, Newfoundland. ~The Eocene of Tete ‘By I RENE 63,7 By A. O. Be ste et AO) FourtTau, Member of Heyptian BN aes ia 8s 90 TE SEIURE 2 - Ill. REPORTS AND PROCEEDINGS. eee for, Wator at Hinckley, ae Liverpool Geological Society 90 Calcium Carbonate and Evolution 2 ue SUP BET SD ENG. 2 in Polyzoa. By’ W. D. LANG, C. S. Du Riche Preller ... 92 fae M. A., ie G. Ss. ints . 73 We OBITUARY. Glacier Lake Gigi ne Pia Dr, Arthur Vaughan, M.A. (P1.V.) 92 fessor PERCY FRY KENDALL. Dr. J. C. Moberg ia ee OO (With a Text-figure. we .. 77 | W. Rupert Jones 96 S The Volume for 1915 of the GEOLOGICAL MAGAZINE is ready, 26 net, Cloth Gases for ‘Binding may be had, price 1s. 6d. net. JAMES SWIFT & SON, Manufacturers of Optical and Scientific Instruments, Contractors to all Scientific Departments of H.M. Home and Colonial and many Foreign Governments. Crands Prix, Diplomas of Honour, and Gold Medals at London, Paris, Brussels, ete. MICROSCOPES AND OTHER INSTRUMENTS FOR ALL BRANCHES OF GEOLOGY, MINERALOGY, PETROLOGY. Sole Makers of the ““DICK’? MINERALOGICAL MICROSCOPES. Dr. A. HUTCHINSON’S UNIVERSAL CGONIOMETER. University Optical Works, 81 TOTTENHAM COURT ROAD, LONDON. 2 vols, 4to. With 28 plates and 137 illustrations in the text, and accompamed by a folio Atlas of 42 maps. Price £3 net. THE IRON ORE RESOURCES OF THE “WORLD. A Summary compiled upon the initiative of the Executive Committee of the Eleventh International’ Geological Congress, Stockholm, 1910, with the assistance of Geological Surveys and Mining Geologists of different Countries. EDITED BY THE GENERAL SECRETARY OF THE CONGRESS. 4to. Sewed. £1 net. CLIMATIC CHANGES SINCE THE LAST ICE AGE. A Collection of Papers read before the Committee of the Eleventh. International Geological Congress at Stockho/m, 1910. DULAU & CO., Ltd., 37 Soho Square, London, W. E GHOLOGICAL MAGAZINE NEW SERIES. DECADE VI. VOL. Ill. No. II.—_ FEBRUARY, 1916. ORIGINAL ARTICLES. I.—On a New Specimen oF tHE Liassic Pacnycormip FIsH SAUROSTOMUS ESOCINUS, AGASSIZ. By A. SMITH WOODWARD, LL.D., F.R.S., Pres. Geol. Soc. (PLATE II.) LTHOUGH the Pachycormid fish Saurostomus esocinus was A known only by part of a lower jaw from the Upper Lias of Baden when it was first named by Agassiz, its principal characters have since been revealed by many incomplete specimens from the Upper Lias of Wiirtemberg, France, and Yorkshire, and by a well- preserved fish from Ilminster, Somersetshire, in the Charles Moore Collection, Bath Museum.! The internal skeleton of the trunk and the fins, however, have not hitherto been so well seen as in a nearly complete fish from the Upper Lias of Wiirtemberg, prepared by Mr. Bernhard Hauff and now in the British Museum. This new specimen, which measures about 1:4 m. in total length, is shown of about one-eighth the natural size in Plate II. The head is deepened by crushing, so that the roof is pushed upwards above and ‘the gular plate downwards below ; but it is obviously shorter and wider than that of Pachycormus, while the snout is comparatively blunt. The external bones are thin and of fibrous texture, and are thus crushed on the stouter inner elements in a confused mass, but - afew features are recognizable. A notch in one bone which seems to be nasal may be regarded as marking the narial opening. The blunt rostral region is shown in front view, with a row of small conical teeth along the oral border as already observed in a Whitby specimen. The large orbit is indicated by an ossified sclerotic in two halves, anterior and posterior. The cheek-plates are obscured by their crushing on the mandibular suspensorium and pterygo-palatine bones; but it is clear that although the hyomandibular is inclined backwards, the quadrate turns as sharply forwards, so that the mandibular articulation is not far behind the orbit. Below the cheek the long and slender maxilla is conspicuous, a little downwardly curved in its hinder portion, where its upper border is overlapped by a single long and narrow supramaxilla. The maxilla bears the usual large conical teeth in a spaced series, flanked outside by a close series of comparatively minute teeth, as in Hypsocormus. A cluster of rather large teeth, of the palatine or other inner element, is also seen between the maxilla and displaced premaxilla. In the mandible the 1 For references to literature see Catal. Foss. Fishes Brit. Mus., pt. iii, p- 388, 1895; also A. S. Woodward, ‘‘ Fossil Fishes of the Upper Lias of Whitby,’’ Proc. Yorks. Geol. and Polyt. Soc., vol. xiii, p. 158, pl. xx, 1896. DECADE VI.—VOL. II.—NO. II. 4 50 Dr. A. Smith Woodward—On Saurostomus esocinus. angular bone is relatively small, and the dentary is as originally described by Agassiz. The lower teeth of the spaced series are slightly larger than those of the upper jaw, but are similarly flanked . outside by clustered minute teeth. All the teeth are conical, a little incurved at the apex, covered with smooth enamel, and: vertically fluted at the base. The preoperculum, operculum, and suboperculum are vaguely seen, of the characteristic shape. Behind the large gular late there are also traces of the branchiostegal rays. The trunk is distorted as usual, especially just in front of the dorsal and anal fins, which are thus separated a little from their supports. The vacant space for the notochord is widened by this distortion, but most of the arches above and below are well preserved. The total number of vertebral arches is about 110, of which 50 may be assigned to the abdominal region. The ribs are comparatively short and slender, while the neural arches of the abdominal region bear gently curved spines, each forming an irregular node at its fused lower end and tending to slight expansion at its upper or distal end. In the caudal region the simple neural and hemal arches are nearly symmetrical above and below the notochordal space, and sharply inclined backwards. Within the base of the tail six or seven hemals become relatively stout, and the last hemal forms the fan-shaped bone which is so characteristic of the Pachycormide. In the pectoral arch the two supraclavicles are well seen, relatively large, long and narrow, straight, and of conspicuously fibrous texture. The clavicle is obscured, but behind it there are traces of the usual thin and large postclavicular scales. The right pectoral fin is specially well preserved, with at least twenty rays, which do not appear to be transversely articulated but become very finely divided distally. The fourth or fifth and longest ray is gently curved and much longer than the others, which rapidly shorten backwards.’ There is no trace of pelvic fins. The supports of the dorsal and anal fins, which are well preserved though displaced, are remarkable for their great length. Not less than twenty-five or twenty-six of these supports are shown in each fin, all expanded at the end for articulation with the fin-rays. The dorsal fin must have been almost completely in advance of the anal, and the fragmentary remains show that it was elevated in front, comparatively low behind. The anal fin is altogether less elevated, and the articulations of its rays are shown to have been distant. The rays of the powerful forked caudal fin are also articulated only at distant intervals, but are very finely sub- divided distally. Nearly all the scales have been removed from the fossil, but a scattered patch behind the dorsal fin shows that they are small and thin, with some traces of a very fine tuberculation. There are vague remains of the enlarged scale at the origin of the anal fin. Indications of digested food are also seen in the abdominal region. The most interesting feature of this new specimen of Sawrostomus is the remarkable elongation of the anterior pectoral fin-ray, which 1 The pectoral fin from Whitby figured in Proc. Yorks. Geol. and Polyt. Soc., vol. xiii, pl. xx, fig. 2, 1896, thus seems to belong to Pachycormus, not to Saurostomus. ‘mo 69 X ZL 9ZIS “YeN ‘NUGVNZ1IOW *‘SyIT] Utdd{) ‘zusspby ‘SQNTOOSH SONOLSOUNYVS ‘TI divIg ‘QIGL “PVIN “10s F. G. Percival—Punctation of Terebratulid Shells. 51 suggests its use as a tactile organ. Although stich elongation is not uncommon among modern Teleostean fishes, it does not appear to have _ been observed hitherto among Mesozoic Ganoids. I may also add that some of the bones, such as the supraclavicle and the neural arches fused with their curved spines, are exact miniatures of some of the bones of the gigantic Leedsia problematica from the Oxford Clay. They therefore tend to support the opinion that this largest known Mesozoic Ganoid belongs to the Pachycormide. EXPLANATION OF PLATE II. Saurostomus esocinus, Agassiz; nearly complete fish, about one-eighth natural size. Upper Lias: Holzmaden, Wiirtemberg. British Museum No. P. 11126. Prepared by Mr. Bernhard Hauft. Il.—On tHe Poncrarion oF THE SHELLS or ZeRERRATULA. By F. G. PERCIVAL, B.Sc., F.G.S., Assistant Lecturer in Geology at the University of Manchester. (PLATE III.) ile 1844 Carpenter [1] divided the fossils then known as Zerebratula into two groups—a perforate group, having the test covered with ’ minute pores, and an imperforate group (the Rhynchonellids). These perforations (see Plate III) correspond to tubular processes of the mantle. Sharpe [2] suggested that these cecal processes of the mantle had a respiratory function; but the shell is covered with a chitinous periostracum which is imperforate. Carpenter considered this might be cellular, allowing water to pass through. Sollas [3] in 1885 suggested that they were sense organs affected by light, since the - periostracum is transparent. Morse [4] offers the suggestion that they are organs of general sensibility. The tubules are not of uniform diameter throughout. The inner half, near the mantle, according to King [5] is narrow, the outer half wider, with a sudden dilation at the ‘mouth’. From the mouth a number of fine lines or tubes radiate. It is interesting to note that from the outer lip of each cecal process a number of fine cilia radiate. Possibly these cilia fit into the radiating tubes (see Morse [4]). The radiating tubes are rarely seen in fossils. An example is shown in Pl. III, Fig. 3. In some forms, e.g. 7. punctata, Sow., the puncte are elongated and slit-like at the outer surface, but have a round cross-section a little farther in. This is well shown in Fig. 5, where part of the outer layer has flaked off. In Zerebratulina (Fig. 1) the cecal tubules branch as they pass outwards, but I have not observed this in any species of Zerebratula. It would, however, be difficult to recognize in fossil specimens, even if present. The examination of the puncte, or external openings of the tubules, was first undertaken ‘with the hope of using their variations as aids in distinguishing species. The puncte are arranged in rows roughly parallel with the growth-lines. When the apertures are slit-like the long axis of each slit points to the umbo, and this emphasizes the fact that they are also arranged in rows radiating out from the umbo. 52 F. G. Percwal—Punctation of Terebratulid Shells. Where the shell is smooth one may find either a square or a quin- cuncial pattern, but this regularity is broken by the subdivision of the rows, both transversely and radially. There is a tendency here and there for the lines to become very irregular, the radial rows ‘streaming out’ into many branches. This occurs, Mr. J. W. Jackson informs me, particularly along the muscle impressions. In the gerontic stage the transverse lines are no longer in sweeping con- tinuous curves, but are broken up into many little wavelets, and it is very difficult to count them. With regard to the size of the puncte, one can distinguish roughly between coarsely and finely punctate shells, but nicer distinctions are unreliable, since the shapes of the individual puncte depend very largely on the amount of wear the shell has suffered; e.g. in T. punctata, Sow., an unworn shell may show long slit-like puncte, while a more worn test has rounded pores. Usually the puncte are hollows, but in specimens that have been naturally etched the material filling the puncte may project beyond the general surface level. Sometimes the ‘walls’ of each punctation project slightly, forming a small tube-like process. But all these differences may occur in one species, or even in different parts of one individual, and are therefore useless for our purpose. The only other convenient means of distinction by puncte is the variation in the number per square millimetre (or ‘density’). If the various species have sufficiently different densities this would be a valuable aid in specific determination. It is already so used to some extent." There is a gradual increase in the density from the umbo outwards to the anterior edge. The following readings are typical— T. biplicata (Brocchi) (a) 93, 111, 115, per sq. mm. (6) 72, 75, 86, 98, per sq. mm. (c) 68, 62, 81, 92, 112, per sq. mm. (d) 49, 54, 67, 90, per sq. mm. T. aff. crickleyensis, 8. Buckman, 224, 292, 344, per sq. mm. In each of the above five examples the first reading was at about 1:5 cm. from the umbo, the other numbers being progressively farther out. Not all of the individuals show such big variations, and. this increase is not always regular. Occasionally there will be a decrease in: density over a zone a few millimetres wide (see example ¢ above). Again, when a strongly marked growth-line intervenes there is usually a sudden change of density. This is to be expected if there is a continuous variation from youth to age, a variation which is maintained even during the period of slow growth or cessation of growth represented by such a strongly marked growth-line. In 7. diplicata (Brocchi) the rate of increase is more rapid towards the sides than towards the anterior along the median line. This is obviously because the shell is longer than it is broad; hence growth takes place more rapidly at the anterior edge than at 1 See e.g. F. Blochmann, Die Brachiopoden der Schwedischen Siidpolar- expedition, Stockholm, 1912, and J. W. Jackson, ‘‘ The Brachiopoda of the Scottish National Antarctic Expedition ’’; Trans. Roy. Soc. Hdin., vol. xlviii, pt. ii, No. 19. F. G. Percwal—Punctation of Terebratulid Shells. 538 the sides, and one travels over the stages from youth to age more quickly in an oblique direction than along the median line. The variation is negligible along any particular zone of growth parallel to the growth-lines. It follows from the foregoing that one must always choose some fixed part of the test for the counting. In the earlier work the valves were divided into squares of one centimetre, commencing at the umbo, the lines being painted in water-colour. Readings were taken in the second square, i.e. at between one and two centi- metres from the umbo, on the dorsal valve when possible, otherwise on the ventral. The figures for the ventral valve are approximately the same as for the dorsal. If the density'is to be of any value the range for a species must not be very great. But it appeared in one or two cases that there was a rather large variation. Moreover, as previously mentioned, occasionally a sudden change occurred. For example, a specimen of Microthyris sublagenalis, Davidson, showed in the first square centi- metre a band where the density rose suddenly from 168 to 272 (see Pl. III, Fig. 2). A strong growth-line separated the two readings, but farther out, in the third square from the umbo, the density had fallen to 152. Obviously, if irregular variation like this is at all common there will be a big range for each species, even if we confine our readings to a spot of very small area at a fixed distance from the umbo in each example. In order to test this large numbers of two species were collected. The first was 7. beplicata “(Brocchi), using the term in Davidson’s broad sense, of which 166 examples were obtained from the Manchester Museum collection. All were from one horizon and loeality—Lower Chalk, Sewell. There was a fairly wide variation in form, but there was a complete gradation among them. Over 300 specimens of 7. punctata, Sow., were also collected from a couple of blocks in a Middle Lias quarry at Stathern, Leicestershire. In these specimens the puncte were usually beautifully preserved and yet difficult to count. Staining did not improve them at all. Most of them had transparent shells with a black matrix inside and filling the puncte. The matrix showed through the test, and the puncte were almost invisible against the dark background. On heating the fossils on wire gauze over a Bunsen flame the tests cleaved into myriads of tiny rhombs, giving an opaque white appearance against which the black puncte showed very distinctly. After heating, the surface was covered with Canada balsam to prevent flaking, but in some cases it was an advantage to let the thin outer layer flake off, as the round cross-section of each punctation in its inner half made a very distinct spot, easy to count. At first photomicrographs of known magnification were taken, but this was too slow a process. The later work was done by using a long extension camera, giving» an image magnified fourteen diameters. A square of 14 millimetres was cut out of a sheet of paper, which was then moved into various positions on the screen. With the aid of a lens several readings were thus taken for each individual, by counting the numbers in the square. These readings 54 F. G. Percival—Puncetation of Terebratulid Shells. were averaged. In order to keep approximately to the same area in each case a circle was drawn on each specimen. The range in each of the two species was very great. There is no reason to suppose that they are in any way abnormal. In 7. biplicata one individual had a density of only 39 per square millimetre, and one was as high as 129. 7’. punctata ranged from 66 to 240. Thus these two species alone cover a great part of the whole range of variation possible for the genus, and the feature must be of extremely little value for purposes of specific distinction. The following tables summarize the results. It was necessary to group the density numbers in tens for two reasons: first, the actual number of individuals was small compared with the great amount of variation, and secondly, certain numbers tended to predominate owing to the method of counting. In order to count accurately from 100 to 200 tiny spots within a square of 14 millimetres one must, if possible, get them arranged in rows parallel with the sides of the square. As a result one often gets, say, eight rows of eight or nine puncte, and so on; i.e. numbers like 64 (8 X 8), 72 (8 xX 9), _ 81, 90, 100, 121, etc., will unduly predominate. So those individuals with a density of from 41 to 50 were grouped together, and so on. TABLE I.—T. pwnctata. (See Fig. 1.) Puncte per sq. mm. Nos. of individuals. 61- 70 5 6 5 js . 5 ; ih 71-— 80 0 a 4 : : ; : 3 81- 90 A ° 6 : B : 0 9 91-100 : 5 5 5 : : : 19 101-110 i 3 : ‘ 5 : 6 32 111-120 A 3 0 i 7 5 6 56 121-130 6 fs 5 is - a , 56 131-140 . A 2 ; 5 A c 46 141-150 3 6 : , 5 * fe 44 151-160 . . $ 3 : & é 41 161-170 5 5 ¢ A 6 i 27 171-180 ‘ s : é : a A 11 181-190 : 5 - 4 - : 7 191-200 A F 3 ‘ 4 201-210 4 211-220 : A é é ; : si 4 221-230 5 3 : 6 , : 3 2 231-240 ili Total . 5) BT TABLE II.—T. biplicata. (See Fig. 2.) Puncts per sq. mm. Nos. of individuals. 31- 40 i iB 5 c $ A ; 1 41- 50 é é 6 5 s 4 ; 13 51- 60 4 5 5 3 5 4 36 61-— 70 : 3 : : 3 : se 413} 71- 80 b z i ; ‘ ; 41 81-— 90 6 ‘ 3 é i : 5 14 91-100 4 : A 5 3 é 10 101-110 3 x A ‘ : s ‘ 6 111-120 F A i 4 : A 1 121-130 A . 5 5 , 4 4 ih Total ‘ = 6G F. G. Percival—Punetation of Terebratulid Shells. 55 The results are shown graphically in Figs. 1 and 2. It will be seen that the curve for 7. biplicata is a simple variation curve, confirming the fact that only one species was being dealt with, and incidentally supporting Davidson’s application of the name to a wide range of forms. The mode occurs at between 60 and 70 per square millimetre. The curve for Z. punctata shows a fairly pronounced hump a little beyond the mode, which lies between 110 and 130. Fie. 1. 6 setae ae t s ae ~ 50 .70 90 uo 13Q 450 170 190 210 230 250 30 20 0 30 40 50 60 70 60 90 100 “1a 120 (30 Fie. 2. Fic. 1.—Curve showing variation in number of puncte per sq. mm. in 367 individuals of J. punctata, Sby. Abscisses = puncte Be: sq. mm. Ordinates = numbers of individuals. Fic. 2.—Curve showing variation in number of puncte per sq. mm. in 166 individuals of T. biplicata. 56 F. G. Percival—Punctation of Terebratulid Shells. This may imply the oncoming of a variation, but possibly it may mean that the mode of the specimens from this locality was a little lower than the mode for the species as a whole. If, for example, the mode for the whole species were 150, and the mode for this particular locality between 110 and 130, one would expect the numbers of individuals with a density of 130 to 150 to be greater than those with density 110 to 90, i.e. the curve would slope down more gently to the right of the mode than to the left. In conclusion three points may be emphasized: (1) The shapes of the individual puncte depend to a great extent on the state of preservation of the test, since the shape of the cross-section of a punc- tation often varies as it passes outwards, from circular to oval or slit-like. (2) There is in general a progressive increase in density from the umbo outwards, which is approximately the same in each valve. This increase is not always regular; occasionally the density will decrease for a while, and at the larger growth-lines there is usually a sudden increase. (3) The amount of variation in a species is so great as to make the density almost valueless as a specific character. I wish to offer my grateful thanks to Dr. A. Morley Davies, Dr. G. Hickling, and Professor H. H.Swinnerton for the advice and help they have given at various times during the rather tedious work on which this paper is based. EXPLANATION OF PLATE III. Fig. 1. Dyscolia crossei, Day. Recent: Japan. Middle of ventral valve photographed from outside, showing branching punctations. The forks point to the umbo. (This is the case in all Terebratuline I have examined, though Fischer & (hlert, in describing this species, state that the canals are directed obliquely ‘‘ d’arriére en ayant .)) x 485 », 2. Microthyris sublagenalis, Day. Bathian: Marquise, Boulonnais. Dorsal valve, less than 1 em. from umbo, showing a sudden increase of density from 168 to 272 per sq. mm. x 20. », 3. LT. punctata, Sow. Middle Lias: Stathern, Leicestershire. Portion ‘ of test showing ‘‘radial canals’’ at outer aperture of each punctation. x 40. » 4. TL. punctata, Sow. Flake of shell by transmitted light, showing puncte with circular cross-section, changing to slit-shape at the outer surface. x 40. » oO. TL. punctata, Sow. Test by reflected light. A thin outer flake is removed to show the round section of each punctation towards the inner surface of the test. x 14. REFERENCES. 1, CARPENTER (Dr. W.). ‘‘On the Microscopic SUN: of Shells’’: Rep. Brit. Assoc., 1844, pp. 16-18. 2. SHARPE (Daniel). ‘‘On Trematis’’: Q.J.G.S., Fol: iv, p. 67, 1848. 8. SoLuas (Professor W. J.). ‘‘ Notes on the Cxcal Processes of the Shells of Brachiopoda interpreted as sense-organs’’: Sci. Proc. Roy. Dub. Soc., N.S., vol. v, 1886-7. 4, Morse (E.S.). ‘‘On the Embryology of Terebratulina’’: Mem. Boston Nat. Hist. Soc., vol. ii, 1871-8. 5. KiNG (Professor W.). ‘‘ On the Histology of the Test of the Class Pallio- branchia ’’: Trans. Roy. Irish Acad., vol. xxiv, p. 439, 1867. Grou. Maa., 1916. Pratm IIT. oa: ate figs ts 4 Bs ey 3 ‘ bg C9 itt tT, aw» iM its TEREBRATULID SHELL-STRUCTURES. . ; Lad ; f M ; 3 : fy ej “4 ~ u ‘ : 1 ! F ; ; R. M. Deeley—The Thames Valley Gravels. 57 IJ1.—Tar Frouvio-etactan GRAVELS oF THE THAMES VALLEY. By R. M. DEELEY, M. Inst.C.H., F.G.S. (WITH A FOLDING MAP, PLATE IV.) CAREFUL examination of the distribution of the high-level gravels and sands of the Thames Valley, especially those associated with the boulder-clays, shows that in pre-Chalky Boulder- clay time, not only were the main valley lines marked out, but many even of the smaller valleys, such as the Brent, were in existence. Of course, during Pleistocene time, denudation has been very active ; for over large portions of this area the boulder-clays, gravels, and sands now only occur as scattered patches. Denudation has been most active in the valleys of the main watercourses, less so in the smaller watercourses, and least in the neighbourhood of ridges and high land. However, even in the main valleys, where the deposits were chiefly gravels and sands, the gravels and sands have protected the softer rocks below them, with the result that the gravels which once occupied the old valley bottoms now cap the hills and higher lands. In many situations the most elevated masses of boulder-clay rest directly upon the older rocks, whereas in lower positions the boulder-clays, especially the Chalky Boulder-clay, generally rest upon sands and gravels. We have here an indication that these sheets of gravel were laid down as extensive fluvio-glacial deposits, their heights above the sea depending upon the slope of the land and supply of material coming from the margin of the ice; or, in the case of valleys up which the ice was advancing and blocking the natural exits, upon the heights of the cols at their ends. It must be remembered that both during the advance and the retreat of the ice-sheets vast volumes of water were thrown off at their fronts. When we consider that the ice which entered the Thames Valley came from the Scandinavian Peninsula, and that the greater portion of the precipitation on the ice-sheet which occurred between England and Scandinavia was liberated as water near the ice fronts, it is clear that an enormous volume of water was given off at the ice-sheet margins. Such melting took place both during advances and retreats of the ice. During the advances some of the precipitation was stored up as ice, and during the retreats some of the ice was melted, and increased the volume of water thrown off ; but when we consider the slow nature of the advances and retreats, and the great length of time the ice-sheets persisted, it is clear that, as far as flood-water from the ice is concerned, periods of retreat did not differ greatly from periods of advance. In the Thames Basin, with the exception perhaps of the estuarine portion, the whole district has been above the sea-level ever since the deposition of the Lenham Beds; consequently subaerial denudation had been active over the district for long ages before the Glacial Period, and there must have been an old river system in existence before the advent of the ice. However, as the directions of the main valleys in the unglaciated areas have always been largely as at present, in spite of the increasing development of subsequent streams, 58 R. M. Deeley—-The Thames Valley Gravels. the old river gravels have been largely destroyed as the rivers cut vertically and horizontally into the land. For many reasons, in the process of excavating their valleys, rivers at various times bring their valley bottoms to base-level. ‘hey then cease to deepen them, but continue to attack the valley sides, and in course of time lay down extensive sheets of gravel. When a pause in vertical excavation persists for a long period, the surrounding high lands, when the rocks are soft, are denuded until we have a country of low relief through which the rivers course sluggishly over wide plains of gravel and of brickearth formed by floods. The gravel deposits of the River Thames show that such pauses in vertical erosion occurred several times, for we have the remnants of several of these gravel plains at various heights, some of them forming terraces along the main river valléys, and others far removed from the present watercourses. However, whilst the rivers were excavating their valleys from one base-level to another, they also formed gravel deposits at intermediate heights. It thus comes about that there are gravel patches at almost all heights above the rivers, but there are masses concentrated at particular levels. During the Pleistocene Period the ice-sheets reached the Thames Basin, and threw into the Thames Valley large quantities of gravel and sand. At these times gravel beds of exceptional thickness and of large area were formed. An endeavour will be made to connect these fluvio-glacial deposits with those of the fluvio-glacial fans near the old ice margins. The suggestion that the pre-Chalky Boulder-clay Thames Valley, especially the eastern portion, was deeply excavated and subsequently partially filled up with fluvio-glacial gravel has already been made by T. I. Pocock.? Bearing in mind the considerations outlined above, by the aid of the excellent Drift maps and memoirs published by the Geological Survey, it is possible to make a preliminary outline sketch of the conditions obtaining in the Thames Valley during the Chalky Boulder-clay stage. To accomplish this object we must proceed from the known to the unknown. In the lower Thames Valley a good deal is known concerning the nature and distribution of the deposits left by the ice-sheet. The unknown is the actual physical condition of the valley in Glacial times; but here we can bring to our aid a knowledge of the nature of the deposits which are being formed by existing ice-sheets and glaciers in such regions as Alaska and Greenland. The most profitable course to adopt in studying such an area as that of the Thames Valley is to obtain, if possible, a knowledge of the deposits formed at some particular stage, and use these as a datum with which to compare older or newer deposits. . When the ice which formed the Chalky Boulder-clay reached the north-eastern watershed of the Thames Valley it discharged into the Thames Basin great volumes of water and large quantities of gravel and sand. The deposits formed in this way contain numbers of rocks foreign to the Thames watershed. During such a time we had 1 Geol. Surv. Summary of Progress, 1902, p. 201. R. M, Deeley del. Wat fans. end. Southchurch, South Valley.” Grou. Maa., 1916. Prats IY. f ROYSTON ay yy) \ \ ! f \ \ MLZ Pr sr ae a EU, Ls Zu Wy Za VLG typ oar in A = ey ‘A CHATHAM ny sg R. M, Deeley del. Fug. F IN) Figher Terrace Gravet. Tilehurst Terrace Gravel. == Ice Margin. Flutie Clme deans 3 x ; TSN) Ye ai S oS — sy ay x} S00 Ft x oe sits x < t i 8 : ~~ 3 } RD BER Ts. S88 ; S 3 3s S SSE k S| i > ya S3 GO 5 MESON TIES 3a Ph = Rave =] = pSX Y aS eS s-8 8 38 Sees i oc Y3s $ SNe 300 S fo Se g Re ~~ re == | _ aS aog ae I —-s4_8 100 —_— O 7.9. ca 30 20 7) o Fg. 2. To illustrate Mr. R, M. Degnpy’s Paper on ‘‘ The Fluvio-Glacial Gravels of the Thames Valley.” 4y J ‘ Mc atitetea Sait toe, all BAT: ‘ t ee F Pal i) =f a ‘\ Py , , : 1 V4 : r fe’. fi . ; d Piet - , wry i ") WR a, , Air eke 4 « / 4 - - i. rs . an BI y 5 yw) ¥ eae : e "i i: . ‘tii 7 5 r he ra ° aie Syiy t ‘ fogs te ie , Sete ers et f', R. M. Deeley—The Thames Valley Gravels. 59 a main valley in which the gravels were deposited over a wide belt, and other tributary watercourses flowing from the ice margin and forming fluvio-glacial fans of gravel and sand. A map showing the probable position of the ice margin, the fluvio-glacial gravel and sand beds in the tributary watercourses, and the area occupied by the fluvio-glacial deposits of the main stream, would furnish such a datum as we require. If the conditions suggested above ever existed in the Thames Valley, then some of the gravel and sand deposits which exist on the hill-tops and valley sides of the Thames may have formed portions of the fluvio-glacial deposits. The Map, Fig. 1, has been constructed to show what were probably the conditions obtaining when the ice which formed the Chalky Boulder-clay reached its maximum extension. A considerable portion of the northern area of the map (Pl. IV, Fig. 1) is occupied by the ice-sheet of the Chalky Boulder-clay. From the various lobes, A to H, powerful streams of water escaped _ down the valleys of the Chelmer, Thame, Colne, Brent, Lea, Roding, and Crouch. These streams formed extensive fluvio-glacial fans, and threw large quantities of water-worn rock debris into the old Thames Valley. ‘I'he probable area occupied by the gravels thus laid down is indicated by the coarse hatching. As the remnants of this deposit now occupy hill tops or shelves on the valley sides and are well developed on the hill on which Tilehurst stands, they have been called the Tilehurst Terrace Gravels. Some gravels, which are probably fluvio-glacial deposits of somewhat greater age, and lie at a higher level, are mapped as Higher Terrace Gravel. When the _ boundaries of the deposits are somewhat uncertain the lines have been dotted in. The dotted line, which runs along the Thames Valley from east to west, and is marked with a scale of miles, is the line of section along which Fig. 2 is drawn. The ice margin has been drawn so as to include the most southerly patches of boulder-clay known. They probably do show the actual limits of the true glacier flow, but some of the lobes may have projected further down the valleys. West of Luton the ice rested near the edge of the Thames watershed. East of Luton the ice crossed the watershed and was arrested by high land in the Thames Basin. Indeed, the outliers of Chalky Boulder-clay show that the margin of the ice-sheet was determined largely by the topography. Here and there lobes of ice pressed through the gaps in the hills. Working from west to east the main ice lobes are as follows :— A. Buckingham Lobe. South of Buckingham there is a gap in the watershed between the Ouse and the Ray in which boulder-clays, gravels, and sands are largely developed. ‘This seems to have been an important line of overflow; for from Stony Stratford past Buckingham to Charndon the overflow valley is well marked. B. Leighton Buzzard Lobe. Here the ice stream curved round the hill to the south of Woburn and travelled as far at least as Leighton Buzzard. C. Dunstable Lobe. At Dunstable there is a gap between the Chilterns and the high ground to the north-west, through which ice 60 R. M. Deeley—The Thames Valley Gravels. passed. Whether the Leighton Buzzard and Dunstable lobes ever coalesced and passed down the valley towards Aylesbury is uncertain. If they did they may have sent floods down some of the gaps in the Chilterns as well as down the Thame Valley. D. St. Albans Lobe. South of St. Albans there is a large patch of boulder-clay which shows that the ice passed through the gap between Hatfield and St. Albans. The gap has a height of about 250 feet. From the ice which passed through it a great amount of debris was thrown into the Thames Valley down the Colne River, in the valley of which there are wide spreads of gravel, some of the terraces of which are portions of the fluvio-glacial fan formed by the water liberated from the front of the Chalky Boulder-clay ice-sheet. EK. Brent Lobe. The gravels of Dollis Hill and Hendon show that an ice-flow from the north-east passed through a gap north of Hampstead and Highgate into the Brent Valley. - F. Lea Valley Lobe. The main ice invasion of the district covered by the Map, Fig. 1, came down the Lea and Roding Valleys and pushed its front into the then forming fluvio-glacial gravels of the Thames; for at Hornchurch the boulder-clay of this lobe has been found resting below the gravel. It must be remembered that the gravels we are considering and the Chalky Boulder-clay are con- temporaneous deposits. G. Crouch Valley Lobe. A considerable volume of ice mounted the watershed between the Chelmer and the Crouch. Some patches of sand and gravel in the Crouch Valley render it somewhat likely that this valley was occupied by a fluvio-glacial fan which ran in an easterly direction to the Thames Valley. H. Malden Lobe. A lobe of ice passed towards the east, south of Tiptree Heath, and sent out a fluvio-glacial fan towards the north-east. Other ice lobes moved towards the east down the valleys of the Suffolk rivers, but how far north the Thames then ran before reaching the sea is unknown at present. The arrows over the northern portion of the map show the probable direction of the ice-flow. Harmer’ has already given the probable directions of the flow of the ice from the north over the Fenland as far south as Royston. The directions of the ice-flow of the area we are dealing with, as shown on the Map, Fig. 1, are in entire agree- ment with his views concerning the movement of the more northerly portions of the ice. The coarsely hatched area, the greater portion of which follows the course of the Thames River, is the probable area occupied by the Tilehurst fluvio-glacial gravels of the main river when the ice reached its most southerly limits. Along the valley a dotted line has been drawn, and Fig. 2 is a section along this line. The present upper surface of the Thames alluvium is shown by the line AA. The slope amounts to about 2°5 feet per mile. The terraces and patches of gravel we have to make use of to ascertain the levels and thicknesses of the fluvio-glacial gravels of the old Thames River are not very numerous, and are no doubt mere 1 Jubilee Volume of the Geologists’ Association, vol. i, p. 108. R. M. Deeley—The Thames Valley Gravels. 61 fragments of the old deposit. Since these gravels were laid down the Thames has greatly deepened and widened its valley, and in doing so has destroyed the larger portion of the old deposits. When first the water thrown off by the ice passed over the cols and entered the Thames Valley, it may have been muddy; but was free from gravel and sand, these latter being deposited in the valleys up which the ice was advancing, and were subsequently covered up by or converted into boulder-clay. The large volume of water thrown into the Thames Valley would first result in increased erosion and the destruction of much of the old Thames gravel of pre-Chalky Boulder- clay age. However, when the ice reached the watershed, then immense quantities of gravel and sand would be thrown into the valley, and the stream being unable to carry it away the gravel and sand would collect in the valley bottom and form a thick bed. When a river is thus aggrading its valley it does not form one wide stream, but breaks up into a form known as a “‘ braided stream”’. The Thames Valley may be divided into an upper or Oxford Basin above the Goring Gap, and a lower or London Basin below the Goring Gap, the Chiltern Hills and the high ridge to the south-west separating them. } When the ice margin stood on the north-east watershed of the upper basin, gravels were formed at heights of 100 feet or more above the present level of the Thames. However, in the Oxford Basin very cold climatic conditions existed even outside the Chalky Boulder- clay ice margin, and there is a marked absence of stratification in the Plateau Gravels of the region. Even if the ice did not override the watershed at one time, it is probable that heavy snow-drifts collected _on the valley sides in sheltered positions, destroying older gravel terraces and disturbing gravels then forming. In the Geological Survey Memoir for Oxford it is stated that the stones in the high-level gravels are a very mixed collection; among _ them occur numerous partially rounded flints a few inches across, liver-coloured quartzites doubtless from the Bunter Pebble Beds of the Midland Counties, white vein quartz, various coloured quartzites, hard sandstones resembling greywethers, soft sandstones with felspar of the Millstone Grit type, and black lydian-stone. The highest outlier on the Oxford sheet is at Bower’s Hill, 540 feet O.D., but this deposit is doubtless much older than the Chalky Boulder-clay. In the Oxford Basin the Plateau or Fluvio-glacial Gravels are not well developed, having suffered very considerably from the erosive action of the rivers and streams, and perhaps from the collection and movement of snow masses. However, there are some outliers of gravel, etc., at levels of 300 feet above O.D., which would appear to belong to the series formed whenthe Chalky Boulder-clay ice stood on the watershed to the north-east. The patches between Ipsden and _ Lewknor, extending along the edge of the Chilterns at heights of 300 to 400 feet above O.D., may be partly of this age; but as they are almost wholly flint gravels formed of materials derived from the weathering of the Chiltern Hills, they may be of various ages. In the basin of the Thames at.Chiselhampton and Great Milton, there are patches of gravel at heights of about 290 feet above O.D. 62 hk. M. Deeley—The Thames Valley Gravels. which may be connected with fluvio-glacial fans which came from the Leighton Buzzard and Dunstable Lobes, for they both contain pebbles of the Northern Drift. Patches of gravel at about the same height also occur in the neighbourhood of Oxford, ete. The drift deposits in the north-western portion of the Map, Fig. 1, have not been surveyed in detail, but enough is known to show that large fans of fluvio-glacial gravel from the Buckingham Lobe occur there. Owing to the fragmentary nature of the drift deposits in the Oxford Basin, and the fact that some areas have not been mapped in detail, the probable distribution of the fluvio-glacial deposits of this district have been drawn in dotted lines. The evidence furnished by these much disturbed and denuded high-level gravels is to the effect that when the Chalky Boulder-clay ice poured its debris into the Oxford Basin of the Thames Valley, portions of the basin had been denuded so as to form an extensive flat area which now stands about 300 feet above the sea. Over this area the fluvio-glacial gravels were spread in a great sheet covering such of the old river gravels as remained, and also the surrounding low country. The floor upon which the gravel rests is now wonderfully level, the slope towards the outlet of the Oxford Basin at Goring being quite small. The 300 feet fluvio-glacial gravels of the Oxford Basin may have been fifty feet thick, as they are further down the river; but mere fragments of them remain. When a terrace is spoken of as being the 300 foot terrace it must be understood that the gravel and sand rest upon a platform of older rocks whose upper surface is at a height of 300 feet above O.D. During the Chalky Boulder-clay period there must have been a very large stream of water flowing through the Goring Gap, a stream which partially dried up in the winter months. With this stream came Bunter pebbles into the London Basin, thus accounting for their presence to the west of points where they also reached the area from the St. Albans Ice Lobe. On Fig. 2 the heights above the sea and thicknesses of a number of these outliers of gravel inthe London Basin are plotted. The fluvio- glacial and other old gravels of this area, although the district has suffered much denudation, are less fragmentary in character than in the Oxford Basin. Indeed, they cover very considerable areas and their arrangement is much more easily traced. In Fig. 2 the dotted line BB shows the average height of the bed upon which the ‘schotter’ formed by the ‘ braided streams’ rested, whilst the line C C shows its upper limit. These levels must only be regarded as approximately correct. The gravel beds must have varied very considerably in thickness, often finishing off as a feather edge on the slopes of the valley sides. The gravel and sand patches which have been used to draw these lines are shown on the section, being named after some small town, village, or hill. The heights have been ascertained as closely as possible either from Ordnance Survey contoured maps or from the Drift coloured maps of the Geological Survey. In the Thames Valley, east of Goring, and generally capping the higher Tertiary hills, there are deposits which Whitaker has called R. M. Deeley—The Thames Valley Gravels. 63 the Pebble Gravel. The pebbles are well water-worn, and consist of flint, quartz, and quartzite. They are certainly much older than the Chalky Boulder-clay, as can be seen from the relationship of the two deposits near Potters Bar and the region immediately to the north- east. On Fig. 2 the dotted line D D shows the general slope of these Pebble Gravels to be about 4:4 feet per mile as we goeast. However, the direction of the section is not quite along their dip slope. At one time the Pebble Gravels must have been a wide-spread deposit, but whether they are the remnants of the gravels of an old river and its tributary streams is uncertain. It is owing to the protection the gravels afforded to the soft rocks below that the deposit now occupies high ground above the softer surrounding rocks. At much lower levels, and sloping in somewhat the same direction as the Pebble Gravel, we have what are here considered to be the fluvio-glacial gravels and sands of the Chalky Boulder-clay ice-sheet. They stand at heights which lie roughly, as previously stated, between the levels shown by the dotted lines B B and CC, Fig. 2. In Fig. 1 the coarsely hatched area of the Tilehurst Gravels shows the ground which was probably occupied by the fluvio-glacial gravel of the Chalky Boulder-clay period. It is suggested that the bottom of the valley was then flat, denudation having reduced the level of much of the surrounding soft rocks to base-level, the whole area, where it was sufficiently low, being covered by a thick sheet of gravel. There may have been numerous ridges, low hills, and gravel terraces standing above the plain which were not covered by gravel, consequently the whole of the hatched area may not have been covered by the deposit. In the neighbourhood of Goring the base of the gravel stands at ~ about 3800 feet O.D. Up the Kennet Valley it is a little higher, whilst it falls rapidly in an easterly direction. On this account it is not convenient to call the deposits the 300 foot terrace, and they will be referred to as the Tilehurst ‘errace Gravels for distinctness. At about ninety-four miles from the margin of the map, Fig. 1, there is a deposit of gravel and sand on the hill to the west of Tilehurst. Its highest point and the level of the rock terrace on which it rests are indicated by the vertical line. Monckton! describes this deposit, and some of the other gravels to be referred to, as glacial gravels, and states that they contain quartzites, large blocks of quartz, and igneous rock. By the Geological Survey they are described as being as a whole ‘‘distinctly current-bedded, though this character is more conspicuous in some pits than in others”’. In the Kennet Valley on the ridge to the north-east of Beenham, at nearly 100 miles, there is gravel and sand at about the same level as at Tilehurst. Other high-level gravels at Sonning, Finchampstead, Hurley, Bisham, and Winter Hill belong to this terrace. From Flackwell Heath to Harefield the deposits plotted are those of the St. Albans Ice Lobe, glacio-fluvial fan gravels and sands. In 1 Q.J.G.S8., vol. xlix, p. 309, 1893. 2 The Geology of the Country around Windsor and Chertsey (Mem. Geol. Surv.), p. 60. 64 - René Fowrtau—The Eocene of Egypt. the Colne Valley, 3 miles south of St. Albans, is a patch of Chalky Boulder-clay resting upon sand and gravel. The gravel comes down to a level of about 230 feet, and the Boulder-clay les between the levels 250 and 290 feet or thereabouts, whilst the same deposit of gravel is from 310 to 335 feet high on the other side of the river to the south-east. The presence of a patch of Boulder-clay up the Colne River, 12 or 14 miles from the Tilehurst Terrace Gravels, and almost as low down as the section line BB, Fig. 2, is remarkable. However, the fluvio-glacial gravels near the Boulder-clay patch rise as high in places as the section line C C where it passes the confluence of the Colne River and the Thames. It would appear that the Chalky Boulder-clay ice built up in front of it a mass of gravel and sand whose upper surface was considerably above the lower level of the ice and boulder-clay. When this takes place and the glacier is retreating, large masses of glacier ice are left beneath the gravel plain, and these melting out form great pits in the alluvial deposits. Such a condition of affairs may now be seen in the valley of Hidden Glacier,’ Alaska. (To be concluded in our next number.) TV.—Tue Divisions or tHe EKocenr or Eoypr AS DETERMINED BY THE SuccEssion oF THE Ecutnip Faunas. By RENE Fourtavu, Member of the Egyptian Institute, etc. VERY remarkable fact in the paleontological study of the Eocene strata of Egypt is the succession of echinid faunas, which seem definitely localized at well-determined horizons, enabling these to be recognized with ease. The opening of the Eocene period is marked by the appearance of a group consisting of Conoclypeus Delanouei, de Loriol, Plesio- spatangus Cotteaut, de Loriol, Linthia cavernosa, de Loriol. C. Delanouet characterizes the strata to which the Egyptian geologists have given the name of Libyan. L. cavernosa appears almost at the same time as C. Delanouei, but disappears earlier ; it is no longer met within © the upper beds of the Libyan stage, which are characterized by the abundance of Foraminifera of the genus Alveolina, and in which a new echinid fauna is recognized. Finally, Plesiospatangus Cotteaut occurs only in the central portion of the Libyan stage. In addition to these three very abundant species, others of less frequent occurrence may be mentioned. Such are Opzsaster thebensis, de Loriol, exclusively restricted to the lower part of the Libyan stage; the group of Megapneustes (IL. Sickenbergerit, Mayer-Kymar, M. Lorioli, Gauthier, If. grandis, Gauthier), and Linthia Delanouet, de Loriol, which are only met with in the central portion. The upper part of the stage, which has received the special name of the ‘‘ Alveolina Series’’, contains, in addition to C. Delanouet, Lichinopsis libyca, de Loriol, Eehinolampas Humet, R. Fourtau, Sismondia Logotheti, Fraas, Hypsospatangus Lefebvrer, de Loriol. C. Delanouei is represented at this horizon by a somewhat peculiar 1 The Yakutat Bay Region, Alaska, by R. 8S. Tarr, p. 63. René Pourtau—The Hocene of Egypt. 65 variety in which the periproct is unusually developed, tending to be nearly as broad as it is long, and penetrating the posterior border; E. Humet, very rare below, abounds in certain localities ; S. Logothett is restricted to the ‘ Alveolina Series’’, but only in the south; to the north it is replaced by S. varians, R. Fourtau, which is also limited to this horizon. Z. libyca and H. Lefebvrei are among the most characteristic forms and are present almost every where. In addition, the ‘‘ Alveolina Series”? yields a number of forms which are only prevented by their very narrow localization from being characteristic: such are Levocidaris miniehensis, Mayer- Kymar; the genus Gisopygus (two forms of which appear ata slightly lower horizon), which attains a splendid development in the ‘‘ Alveolina Series’’, to disappear almost completely with them; ephrenia Lorio, R. Fourtau, Schizaster miniehensis, R. Fourtau, Huspatangus Lamberti, R. Fourtau, and Cheopsia Mortensent, R. Fourtau. Thick masses of limestones containing enormous numbers of Nummulites gizehensis, Khr., appear above the ‘‘ Alveolina Series ”’ in Egypt. With them, the echinid fauna changes absolutely. The species we have just mentioned disappear, making way for others which have not yet been found in the lower strata. These are: Porocidaris Schmidelui, Minster, Hchinolampas africanus and its variety Mraasz, de Loriol, Schizaster africanus, de Loriol, S. moqatta- mensis, de Loriol, Huspatangus formosus, de Loriol. These forms are met with throughout the mass of limestones with Vummulites gizehensis, accompanied according to locality by less abundant species such as: Levocidaris Abbater, Gauthier, generally distributed, Brisso- _ spatangus Hume, R. Fourtau, in the southern area, Orthechinus mogattamensis, Cotteau, and Brissopsis Lamberti, Gauthier, in the northern portion. Then follow a whole series of limestones in which no echinids have been found. They are characterized by the . abundance of branching Bryozoa and Serpule. _ The strata above these limestones are almost lacking in Nummulites, but yield a special sea-urchin fauna, including: Rhabdocidaris Gaillardoti, Gauthier, Thagastea Luciani, de Loriol, Eehinolampas Cramert, de Loriol, Anisaster gibberulus, Michelin. To these may be added the following species, which are more rarely met with: Thylechinus libycus, R. Fourtau, Echinolampas moelehensis, R. Fourtau, in the southern area, Sismondia Blanckenhorni, Gauthier, and Clypeaster Fourtau, Lambert (=C. Breunigz, de Loriol, non Laube), in the northern portion. Above these deposits is a series of marly or calcareous strata without sea-urchins, and in the Fayum mainly containing vertebrate remains. These successive faunas enable us to establish definite divisions for the Eocene of Egypt. In the first place, we can define two main divisions of which the line of demarcation is easily traced in consequence of the disappear- ance of Conoclypeus Delanouet and the appearance of Hehinolampas africanus, which inaugurates the group of conoclypeiform Echinolampas, apparently derived from C. Delanouev. DECADE VI.—VOL. II.—NOo. Il. 5 66 René Fourtau—The Eocene of Egypt. This demarcation line also corresponds with a notable change of facies and with the appearance in Egypt of the large Nummulites constituting the JV. gizehensis group. ‘These two divisions have been long established and adopted almost unanimously by geologists who have studied the Kocene of Egypt. They are the Libyan and Mogattamian Stages. The Libyan Stage can be subdivided into— 1. Lower Libyan, where C. Delanouwec is present alone with Linthia cavernosa. 2. Middle Libyan, in which with C. Delanowei and L. cavernosa appear Plestospatangus Cotteaui and the group of Megapneustes, which is only found at this horizon. 3. Upper Libyan, long ago separated under the name of ‘‘Alveolina Series’’, which still contains some C. Delanouet, but none of the other species. These are replaced by small forms, of which the most abundant is Hypsospatangus Lefebvrer. The Mogattam Stage, which following the rules of nomenclature we should term Moqattamian, can be easily divided into two sub- stages— 4. The Lower Moqattamian is characterized by large conoclypeiform Echinolampas, together with Schizaster africanus and Huspatangus Sormosus. 5. The Upper Moqattamian in which the sea-urchin species of large size are replaced by others that are quite small, such as Thagastea Lucian, Echinolampas Cramert, Anisaster gibberulus, accompanied by Schizaster vicinalis, Agassiz, while in the uppermost layers the genus Clypeaster appears for the first time in Egypt. The synchronization of the local divisions is somewhat delicate, and has of late given rise to somewhat lively discussion. The Echinids have not been used to establish the divisions adopted in Europe, and latterly efforts have been mainly applied to determining a Nummulite scale, which, it must be admitted, has given good results in many places, but which might give rise to criticism when applied to other localities and especially North Africa. It is not easily to be explained, for instance, why, in Tunis and Algeria, the beds with Mummutlites. gizehensis are attributed by everybody to the Lower Eocene, whereas in Egypt all agree as placing them in the Middle Eocene. The study of the Cercthium group has given fairly good results in the Paris Basin, but division on such a basis is impossible in Egypt, where these Gasteropods are rare, and when present are usually distinct species. It might be therefore useful to take the succession of echinid faunas and changes of facies as our basis in attempting to subdivide the Eocene of Egypt, and to attach only a relative value to synchronizations founded on widely separated faunas. The Table (p. 67) indicates the solution which appears to me the most satisfactory. The synchronizations which I propose in this Table appear to me rational. There might, however, be discussion as to the desirability 67 René Fowrtau—The Eocene of Egypt. ‘UBLISUOT, pue UVIPN'yT “UBIUO}IB “UBISTOANY “UBIyOINT ‘UBISIND “UBIUIPUOT< to uviserd yz “SUIBUIOL OYRIG}IOA TIM spurs AylV{ “Speq snooavo [Wo 90S YIM sprByy ‘s[reu snoosdis pus Ayes Jo spaq yoryy Aq poyeredes ‘satto,seuTT snosdi[is 10 AjrvUE UMOIG *smyn.ieggub sajswsviyy ‘suswayajaow “iy “Vou sodiumjouryon “nnjinoy dajsvediyn ‘vwu1oyuaeyounrg pipuousig ‘wupiny vaysvboy 7, ‘snohqu smunyoojhyy, ‘“wyopimpypwy srpr0pqny ry ‘geuojsounty APART ‘aindiseg pus vozodig JIA SoMOISOUTIT OTT AL “OI}IMOONBIS SSO] 10 910TH ‘SOUOJSOUI] OTFI[MUIUAIN NY ‘NWI 000Q] F YAIAM popAoro uit Jo speq suros YJIA SOUOJSOUTT] OFITT AA “SOTLOJSOUIT] Ayre A194 *sttoTjer0m00 (UIP, UJI souojsourrry *speq ATIVUL OUIOS [ITA “SHIMHS IVYHNAY) GHL NI INGTVAINOD “UBIUOSSONG | SOUOJSOTIT] SNOSOTTIS o41T AA *SnorezT[Issoy ATOA “UBTJOUBYT, | JOU ‘Seto;SoUMIT sNoOedTTIG *SHTOV A “snsou.of snbunyodsnmy ‘sisuawpz90b -0UL “Gi ‘snuporifp sajsmzyoy ‘1saquin'T sisdossuug = “‘vowunzT «= snbunzodsosswug “sDD4T “IBA pues snuporifo spd) -OULY OTT ‘SisuaUD}IDboU snUryoey7z1O “Vwyap “NUYS siuoprvw010g ‘LaIMgQH siippro0iaTy “wuasuai.opy pisdoeyp ‘y4aquiory snbunjodsnm ‘siswayarwurur daysnzvyogy ‘yor.iory niuawyday ‘snbid -OSi‘) SUUAD OI) ‘susuayaruruL sL“ppLd0LaTT ‘YaUNTT spduunjowmyony ‘supra "Sy ‘ayy -obo'T wypuorusig ‘rasagafaTT snbungnds -osdiyT ‘vbfidosopim “1s “anounjagq ‘— yy ganf -UVaNYIG Lajspriuazy ‘vwuoiag snbunyodsnmy “UnUuoy smnpisspp ‘searsnaudpvbayr snued 9} “wzanounjag wiyjzwT ‘wnvajj0p snbunpodsorsa) J ‘psousanna''y ‘vanounjaq ‘O ‘YANG DULOIsOM)D ‘siswaqay) ajspsidC, ‘DsOUdannD DIyIUYT “vanounjag snedhjo0u0p “UBTUIV}YBbOTT “TNHOOU soddq Wadd), = o Ko) Ee ee ee ee E, is) 2 “UBITUER}} BOTT | “ANHOOD TOMO | | a@Taary Jessel | | suvdkqiy reddq | [NIT HO | ANHOOW WAMOT ‘uvkqiry OTPPH | "uvdqiTy TaMorTy | “YNOVY CGINTHO i ‘SHOVLG NVILdAD 68 A. J. Pickering—Borings for Water of including the Bartonian and the Ludian in the Middle Eocene, and of only beginning the Upper Eocene with the Tongrian. The stratigraphical divisions adopted in Europe correspond to marked oscillations of shore-lines, and their delimitation is easy. It is not so in the Mediterranean Basin and especially in its southern part, which, during the whole of the Eocene period, was a region of continuous sedimentation. I have thought that the sea-urchin faunas could help us to establish subdivisions, and have given the result of my researches without stopping at simple questions as to where the brackets representing individual divisions should be drawn. I am greatly indebted to Dr. W. F. Hume, F.G.S., etc., Director of the Geological Survey of Egypt, for kindly translating this paper into English. V.—On two Bortnes ror Water at Hinckiey, LEICESTERSHIRE. By A. J. PICKERING. HOUGH Hinckley is now possessed of an excellent supply of water brought from the Lower Keuper Sandstone of Snarestone, in North-West Leicestershire, up to 1891 it had an unenviable reputation for abortive water-schemes. Some £20,000 had been spent in considering eighteen different propositions and in carrying out three deep borings within a few miles of the town. During this time six consulting engineers were called in by the local authority. All these schemes failed, not through any lack of water—for this was obtained from the Waterstones of the Lower Keuper in almost unlimited quantity—but because it was found impossible to shut out the chlorides and sulphates from the gypsiferous Keuper Marls through which the borings passed. Recently two attempts have been made by private firms in the town to obtain a supply of water from the Upper Keuper Sandstone, but unfortunately these schemes have been abandoned without satis- factory results. The first was carried out for Messrs. Atkins Bros. at the rear of their factory in Bond Street in the centre of the town. Boring was commenced in July, 1913, from the bottom of an existing well 41 feet deep. This had up to late years yielded an excellent supply from the Drift deposits (here about 135 feet in thickness), but had gradually been drained, probably by the sinking of deep foundations in the lower levels of the town and by extensive building operations in the higher levels. This latter would have the effect of diminishing the quantity of rain-water making its way into. the water-bearing drifts. In this boring the jumping-chisel method. was employed throughout; consequently the thicknesses of the beds were somewhat difficult to ascertain. In the following table they must be taken as only approximate. Operations were abandoned in 1914 after repeated attempts to recover a boring-tool, and through the falling-in of the unlined portion of the borehole. The following is the section :— at Hinckley, Leicestershire. 69 WELL AND BORING, BOND STREET, HINCKLEY. (125 yards south-east of junction of Bond Street with Upper Bond Street and the Hollycroft.) 4 Thickness. Depth. Feet. Feet. i Mopysoils : : : : : : : 2 2 2. Chalky boulder- -clay : : : ; . ; . 10 12 3. Sand and loamy sand . : 3 29 41 4, Sand and running sand, light brownish- yellow : 4 11 52 5. Red-brown clay, sandy P : : 5 : : 3 55 6. Grey-brown sand ; , ; ‘ : 3 F 5 60 7. Brown silty clay F : : 10 70 8. Loams and clays, very ‘fine, light- “brown : : : 10 80 9. Brown silty clay (as No. 7) ; : ‘ : : 9 89 10. Reddish-brown silty elBy : : : Be ets : 11 100 11. Dark-brown clay . : ‘ : : : ; 10 110 12. Light-brown clay 18 128 13. Dark-brown oe with pebbles of ironstone and grit and patches of red marl. : : 7 135 14, Light-red marl with green spots and small pebbles” : 25 160 15. Light-green and red marls with thin bands of sandstone 30 190 16. Red marls with green mottling : ; é 8 198 17. Coarse grit . * ‘ 3 : : ¢ 3 201 18. Marls with gypsum . : : : : 22 223 19. Hard grey sandstone, fine- erained 5 : : 2 225 20. Hard red marl . : : 0 : : : 19 244 21. Sandstone (as No. 19). : E : ; : : 5 249 22. Hard sandstone, close-grained . : : : : 7 256 23. Red marl without gypsum . ; : 34 290 24. Red marl with green spots and traces of gypsum . . 10 300 25. Hard red marl . ; : 8 308 26. Harder red marl with conchoidal ‘fracture 2 : . Undetermined. No. 2 is the typical Chalky Boulder-clay of the Midlands, con- taining here a considerable number of Chalk flints and Jurassic fossils; of these the Gryphea arcuata is the most common. It is _ blue-grey in the higher beds, but assumes a redder colour as it approaches the underlying sands. In and near Hinckley it often becomes gravelly, the clay being replaced by a coarse sandy matrix. This gravel is sometimes matted together by a calcareous cement. Nos. 3, 4, 5, and 6 are a sandy series of the Drift, and are, or have been, exposed in many sandpits in and around the town. They vary considerably in appearance, some beds being red and loamy, others pale-yellow and of a ‘sharp’ and crystalline nature; in the latter case the sands weather quickly to a loam on exposure. Interstratified with this sandy series are a few bands of very fine gravel, containing derived shell-fragments in beds of not more than an inch or two in thickness. ‘They also contain thin streaks of black carbonaceous material, probably coal-dust. Current-bedding is conspicuous in all the sands, which are entirely devoid of flints, and are mainly derived 1 Six-inch map, Leicestershire 42 N.E.; one-inch New Series map 169 (Nuneaton); one-inch Old Series geological map 63 S.W. Height above O.D. about 410 feet. Rest-level of water about 80 feet from surface. Pumping-test at a depth of 305 feet yielded 1,400 gallons per hour. Old sunk well 41 feet, new borehole 267 feet; total depth 308 feet. Made by Messrs. Peacock & Bird, Hinckley. Commenced July 23, 1913; abandoned January, 1914. Chisel used throughout. 70 _ Aw SJ. Pickering—Borings for Water from Triassic outcrops. From their position they may be, I think, correlated with the Quartzose Sand of the Lower Pleistocene identified by R. M. Deeley in the Trent Valley. Wherever these sands occur in the neighbourhood of Hinckley they are underlain by thick beds of clay ; consequently they form a natural reservoir and yield a considerable supply of water whenever penetrated below the valley levels. During a recent enlargement of the main sewers in the lowest part of the town these beds of sand were encountered, and the contractors experienced great and unforeseen difficulties in keeping the running sand from their trenches. A large portion of the street subsided as a consequence of the washing away of the underlying sand. Beds 7 to 12 are a series of clays or brick-earths, which are, or have been, worked in several brickyards north, east, and west of the town, e.g. at Messrs. Hudson’s works, Barwell Lane. They are quite free from erratics, save a few small pebbles of quartzite and felsite. Nos. 13 and 14 are the lowest beds of the Drift. They contain a considerable proportion of Keuper Marl material, also numerous Bunter pebbles and rolled fragments of Coal-measure sandstone. Nos. 15 and 16 appear to be Upper Keuper Marls with bands of coarse sandstone or skerry. Nos. 17 to 22 contain a succession of fairly massive beds of Upper Keuper Sandstone of varying degrees of hardness, with an inter- vening 22 ft. bed of mottled marl witha little gypsum. Nos. 28 to 26 belong to the thick lower series of Keuper Marls containing the usual bands of gypsum. The second boring was begun for Messrs. A. EK. Hawley & Co., at their Sketchley Dye Works, early in 1915. After boring 213 feet without any satisfactory results the work was abandoned (for the present) in August last. Unfortunately the first 110 feet were bored by the percussion process, so that again it was impossible to ascertain the thickness of the Glacial Drift with any degree of accuracy. From 110 to 213 feet the engineers used the shot-drill, extracting cores of about 7 inches in diameter. The following is the section :— WELL-BORING, SKETCHLEY DyE WoRKS, HINCKLEY.! (330 yards S. 7° W. of railway-bridge over Rugby Road.) Thickness. Depth. ft. in. ft. in, 1. Top soil, sand and gravel : : : : 2 0 2 0 2. Red clay P : : : 3 : : 8 0 10 0 3. Brown silty clay . : SO. 0 50 0 4. Brown silty clay intermixed with red marly clay 5. Brown silty clay with fragments of red marl, small pebbles of quartzite, and pieces of ~ green sandstone 2 0 15 0 6. Red marl with quartzite pebbles (pebbles larger towards base) 1 Six-inch map, Leicestershire 42 BE. one-inch New Series map 169 (Nuneaton); one-inch Old Series geological map 63 S.W. Height above O.D. about 327 feet. Engineer, Mr. Chas. J. Ell, Luton, Beds. Commenced February, 1915; work suspended following August. . Red marl with a little green marl . Hard red marl : . Green marl . Red marl 3 : : : ; . Red marl with three 2 in. bands of gypsum . Red marl ‘ . Mottled (red and green) m marl with little By psum . Gréen marl . Red marl . Gypsum . Red marl . Green marl . Red marl . Gypsum . Red marl . Mottled marl with eypsum veins . Red marl, calcareous ? . Mottled marl with gypsum veins . Green marl . . Mottled marl, chiefly red . Gypsum . Mottled marl, ‘chiefly red : F . Green and red mar! with sypsum contorted at Hinckley, Levcestershire. bedding-lines . Gypsum x 9 . Green and red marl ; horizontal bedding . Red marl with three bands of eypsum . Red marl - Red marl with veins of gypsum . Green marl é - Gypsum . Red marl . Red marl with thin veins of sypsum . Red and green marl ; . Gypsum : . Red marl . Gypsum . Red marl, slightly mottled . Gypsum . Red marl . Gypsum . Red marl, slightly mottled . Red marl with veins of gypsum - Red marl ; F ‘ : . Gypsum . Red marl . Green marl . . Red mar! with a little gypsum . Green marl . . Red marl with veins of gypsum . Red marl ; : . Gypsum . Red marl . Gypsum . Green marl . Red marl POOR OWNONOROFPNHFONONONODORNOOCOHUWRHROF a FPONOCOHOWFHOHREDRONONANODOW : Thickness, . Clear red marl “ y : : 5 : iyi. . Red and green marls. 21 0 - Red marls with small quantity of gypsum . Hard red marl ‘| ooooconaq SCWWRADWEHEWAROHONOCOCORDS ©& bh Nj 194 198 198 201 201 204 207 207 211 211 211 213 i) e DNOONHEHWOrFANADNINCOOCORAS fe — SWwWoPPWONTRE RE RwWodantoe WoaRWwWHDoODDaHH whip CW WS 72 A, J. Pickering—Borings at Hinckley. It will be noticed that this boring commenced at the bottom of the sandy Drift series. The site being 83 feet below Messrs. Atkins’s boring, the Chalky Boulder-clay was not present. Beds 2 and 3 are the silty clays, and Beds 4, 5, and 6 are the Keuper Drift beds before mentioned. Below these the compact red marls of the Keuper were penetrated, and these continued with interbedded green marls and gypsum as far as the boring was carried. With the exception of indications of contemporaneous puckering in Bed 33 the whole of the cores were horizontally bedded. The absence of all trace of the Upper Keuper Sandstone (either in the sediment of the earlier portion of the boring, or in the cores) is a little remarkable, inasmuch as the site is little more than three- quarters of a mile from the boring at Messrs. Atkins Bros., where beds up to 7 feet in thickness were penetrated. The Holy Well boring,’ begun in 1875 a little farther east, also gave about 30 feet of Upper Keuper Sandstones; but at the Wharf boring,’ 1} miles west of the Holy Well and half a mile west of the Sketchley Dye Works, only 12 feet were present. This absence of the Upper Keuper Sandstone in the Sketchley borehole may be due to one of several causes. Firstly, this sandstone is known to be impersistent at its outcrop in many parts of the Midlands, and is liable in places to thin out, and elsewhere to be split up by beds of marl. There is evidence, too, that more than one band comes in at about this position in the Keuper Marl. Sometimes several bands may be present together in one district, while a little farther on one or other of these bands may thin out. Secondly, although present at the Holy Well and at Bond Street, it may have cropped out against the base of the Glacial deposits before reaching Sketchley. Thirdly, there may be a gentle syncline under Sketchley, by which the sandstone is carried down below the bottom of that boring. This third explanation is supported by the fact that between the Holy Well and Bond Street the base of the sandstone falls 88 feet. If this fall is maintained it would carry the bed below the bottom of the Sketchley boring. It is to be noted that at the Holy Well the distance between the top of the Waterstones (= Lower Keuper Sandstone) and the bottom of the Upper Keuper Sandstone is 217 feet, whereas at the Wharf the distance is 396 feet. It is probable, therefore, that the Upper Keuper Sandstone of the Holy Well thins out or splits up before reaching the Wharf, and that the Upper Keuper Sandstone at the Wharf, 12 feet thick, is a higher band. An examination of the cores showed both the red and the green marls to be entirely devoid of organic remains. The green marls were throughout much harder and coarser-grained than the red, and portions were slightly calcareous. The red marls quickly decomposed on exposure; but the green marls showed little signs of weathering. The usual bands of skerry were entirely absent. The writer is indebted to Messrs. Atkins Bros. and to Messrs. A. E. Hawley & Co. for permission to watch the boring operations, to 1 Rep. Brit. Assoc. for 1875, p. 136; for 1879, p. 160. 2 Ibid. for 1882, p. 226; for 1883, p. 154; for 1887, p. 364. W. D. Lang —Calciwm Carbonate and Evolution. 73 measure and describe the materials brought up, and to put the results on record. This work has been facilitated in every way by the boring firms engaged. For several suggestions and general encouragement the writer is indebted to Mr. T. C. Cantrill, of the Geological Survey. ViI.—Caucruom Carponare AND Evoturion 1n Ponyzoa.! By W. D. Lane, M.A., F.G.S. te a review in the Grotogicat Magazine for 1913? of an important paper by Cumings on the development and systematic position of the Monticuliporoids, it was pointed out that the elucidation of the post-embryonic stages of that group conclusively proved them to be Polyzoa, and disposed of Kirkpatrick’s contention that they were allied to Merlia, a recent siliceous sponge. Thus, further to prove the dissimilarity between the Monticuliporoids and IMerlia is to flog a dead horse. Nevertheless we welcome the excellent figures by Cumings and Galloway of the microscopic structure of the two organisms showing that the skeleton of the one is formed of super- posed layers and the other of radiate spicules so adjusted as to form a mesh-work. The authors, however, are not mainly concerned with the connection of Merlia and the Monticuliporoids, but with the Trepostome wall and various correlated structures, namely Cysts and Cystiphragms, Intrazocecial spines, Acanthopores and Communication-pores. They point out that Communication-pores of Paleozoic Trepostomata resemble those of Heteropora—a form that persists until recent times ;_ ‘that Acanthopores are the continuations below the general zoarial surface of hollow spines, ‘‘ undoubtedly protective’? in function, which, in unworn specimens, project above the surface ; that ‘‘ certain extraordinary spines projecting into the submature region of zocecia “of a species of Nicholsonella’’ resemble those of Heteropora neozelaniea, as figured by Nicholson. They make the very interesting and ingenious suggestion that Cysts and Cystiphragms are the expression of the renewal of the polypide on the formation of a Brown Body (a familiar process among recent Polyzoa) and that the purpose of the ectocyst in laying down a fresh wall at each such crisis is the ‘restriction of intrazocecial space’’; moreover, the occurrence of minute concretions of some iron compound in the Cyst, i.e. the space enclosed by the cystiphragms, is claimed to be produced by the decay of the degenerated polypide. Finally, the structure of the wall is considered. Hitherto it has been customary to divide the Trepostomata by their walls into two groups—lIntegrata, those that have a dark median line in the wall in virtue of which each half is claimed for that zocecium adjoining it— and Amalgamata, in which there is no dark line, but the walls of two 1 [Originally written as a review on ‘‘ Studies of the Morphology and Histology of the Trepostomata or Monticuliporoids’’, by E. R. Cumings and J. J. Galloway, 1915, Bull. Geol. Soc. America, Vol. xxvi, pp. 349-374, Pls. 10-15, but considered more appropriate as an original paper.—ED. | 2 GEOL. MAG., Dec. V, Vol. X, pp. 32-36. 74 W. D. Lang—Caleiwm Carbonate adjacent zocecia are completely confluent. Cumings and Galloway show that this distinction does not hold—that Lee had already remarked that the presence or absence of the dark line was inconstant —and their researches correlate the presence of the dark line with the thinness of the growing edge of the wall and the consequent ‘‘ steep pitch” of the growth-lamine. ‘‘ For some reason, wherever the wall lamine of the trepostomes are sharply bent the material appears dark ... It is probable that the size and arrangement of the minute granules of which the wall laminz are composed differ slightly at such points from the normal size and arrangement in other parts of the wall. In fact, in well-preserved material and in very thin sections it can be shown that this is actually the case.” The similarity of the Trepostome wall with that of the Brachiopoda when they are viewed in thin sections is pointed out, and ‘‘in such sections as are shown in figures 45 and 49 it amounts almost to identity’. Perhaps the most interesting part of the paper concerns the Cingulum or secondary thickening of the wall, and its relation to the secretion of diaphragms and cystiphragms which are clearly shown in the figures to be continuations of this secondary thickening. The authors regard the thickening as an old-age character. ‘‘ The thickening of the interzocecial walls, due to the development of the cingulum, is often very great—far greater than would merely com- pensate for the increasing separation of the zocecia, as they extend radially outward from the axial region. There is an actual reduction \in size of the zocecial chamber; indeed, in some cases, an extreme reduction (figures 1 and 17). We believe that this extreme develop- ment of secondary deposits is a senile feature, analogous to the great thickening of brachiopod shells and the shells of the Mollusca in old age. In recent Bryozoa the zocecia of the older portions of zoaria often become almost or quite filled up with stony deposits, and it seems that the ectosare [ectocyst] may continue to secrete such deposits after the polypide has wholly disappeared from the zocecium.”’ Let us go further. Say that some metabolic process, such as one involved in nitrogenous excretion, resulted in the precipitation of calcium carbonate in the tissues or upon the surface of a marine organism—Mollusc, Brachiopod, or Polyzoan, and was turned to useful account as affording a supporting or protecting skeleton or shell; that this production of calcium carbonate became increasingly constitutional so that the mere need for a skeleton or shell was more than met; that the process could not be arrested or countered in all the organisms that had acquired it, and in these the disposal of superfluous calcium carbonate became a pressing problem; that, finally, those organisms that found no way out of the difficulty were doomed to extinction under a mass of calcium carbonate of their own making. At some time or other most animal phyla have met the calcium | carbonate problem in an acute form. The Protozoa can always crawl away from their skeleton, and many organisms that build tubular shells can similarly move up their tubes which thus become of indefinite length, while tabule, diaphragms, etc., are merely the and Evolution wn Polyzoa. 75 superfluous calcium carbonate of the organism’s after end in its new position. Even Gasteropod Molluscs to a certain extent can behave in this manner. The Arthropods wrestle chiefly with chitin and throw off its accumulation at each ecdysis; but such marine forms as add calcium salts to chitin tend to be cumbered more and more with their exoskeleton at the periodic moults in proportion to the amount of calcium present. Some Molluses, like the Rudiste, have succumbed to masses of calcium carbonate, but the most successful, apparently, have learnt how to circumvent its secretion and produce little or no shell. The point need not be laboured, but this aspect of the deposition of calcareous skeletal matter may help to explain much that is not otherwise clear in the structure and evolution of Polyzoa. The simplest Polyzoa—the less differentiated Cyclostomes—have tubular skeletons, and merely add to the length of their tube, occasionally inserting a diaphragm, and an entombing cap or ‘closure’ may be the moribund act of a senile individual. As the colonies become more massive it is required that the general zoarial surface should remain at the same level, and this could not be attained if each individual independently moved up its tube according to its capacity for calcium carbonate secretion. The forward movement would, therefore, be general and slow, and the deposit of calcium carbonate would be chiefly directed to the interzoccial spaces which generally would tend to widen as the tubular skeletons radiated from a common centre. This is the condition of the more complicated Cyclostomes and the Trepostomes and Cryptostomes in general. But, though the uneven projection of individuals from the surface of the colony is undesirable, skeletal projections that did not interfere with the currents and food supply would not only be harmless, but might even serve a protective purpose. Thus, when the pressure again became intolerable, acanthopores might arise. Again, if the insistence of calcium carbonate was severe, the whole of the ectocyst capable of, yet not actually, secreting would be in a state of unstable equilibrium, an external stimulus might start the deposition of calcium carbonate at any point, and an intrazoccial spine result. Cumings and Davenport do not suggest a utilitarian origin for these. ‘* What possible functions these spines could have we do not venture to say.”” The renewal of the polypide may well have given the necessary stimulus for the formation of cystiphragms and been the excuse for depositing calcium carbonate even if there were no other need for it. Finally, it is unnecessary to look for any special utility in the massive secondary wall-thickening termed by the authors the cingulum, if the whole organism is (so to speak) aching to deposit it. Cumings and Davenport attribute the secondary thickness of the walls to senility of the individual, at least they say it accompanies senility. We claim, further, that it marks the senility of the lineage to which the individual belongs, and it is by turning to harmless or possibly useful account the same ever-present danger that other structures described in this paper are due. Such a conclusion has been impressed upon the writer by the study of Cretaceous Cheilostomes. The Cyclostomes and Trepostomes have been considered. The Cryptostomes divert their excess of calcium 76 W. D. Lang—Caleiwm Carbonate and Evolution. carbonate into the elaboration of secondary apertures. The Cheilo- stomes do the same with marked (temporary) success. But this is only one of their methods. The most hopeful of the Cheilostomes are those which have a skeleton of chitin only. When once calcium carbonate has begun to be deposited the whole lineage is doomed to a more or less stereotyped sequence of calcification until, in the end, it becomes extinguished under its superfluity of skeleton. For obvious reasons it is only these doomed lineages that we have to deal with as fossils; and the evolution of the Cretaceous Cheilostomes, as far as we can have any knowledge of it, is the story of the progressive elaboration of the calcareous skeleton until this becomes secondarily simple by the blotting out of its complexity under secondary deposits. The simplest Cretaceous Cheilostomes—‘ Membranimorphs ’—have calcareous skeletons with no intraterminal front walls.’ Senility in an individual results in the complete calcification of the intraterminal front wall and the consequent death of the zooid, since even the orifice is sealed up. Before this takes place, however, superfluous calcium carbonate, in some forms, is deposited as terminal spines.’ The general phylogenetic future of some of these, namely those in which the terminal spines, arching over, fuse with their opposing and lateral neighbours — ‘ Cribrimorphs ’— can be predicted with certainty, though the details vary in every lineage. Further calcium carbonate is laid down in connection with (1) the spines that form the intraterminal front wall—the coste ; (2) those that surround the aperture—the ‘apertural spines’ (considered with the first pair of cost, those which bound the aperture proximally, and, fused, form the ‘apertural bar’); and (3) the extraterminal front wall, finally filling up the interzocecial angles; and the process may take place in one or more of these directions simultaneously in any lineage. The first method results (with various modifications in various lineages) in a solid, arched, intraterminal front wall; the second (with various interfusions of the apertural spines and apertural bar, often complicated by one or more pairs of avicularia entering into the structure) in a secondary aperture; the third, again often complicated with avicularia, in a generalimmersion of the zocecia beneath interzoecial walls. The secondary aperture may be prolonged after the manner of a tubular fossil (an interesting case of a primitive method revived); but in some lineages the rims of the secondary apertures spread, especially proximally, and, meeting with their neighbours, fuse to form a secondary front wall (lamina peristomica* of Jullien) above the | general zoarial level. Such forms—‘ Steginomorphs ’—though be- longing to various lineages, are generally placed in d’Orbigny’s genus Steginopora, which, thus used, is seen to be a stage in evolution instead of a genus founded on d’Orbigny’s genotypes. It is inconceivable that Steginomorphs can have any evolutionary future. In extreme cases they present externally a thick crust of calcium carbonate pierced here and there by holes representing apertures and avicularia, that tend to become smaller and more choked as more calcium 1 For these terms see Lang, 1914, GroL. MaG., Dec. VI, Vol. I, p. 6. 2 Jullien, 1886, Bull. Soc. Zool. France, Vol. 11, p. 609. Professor Percy Kendall—Glacier Lake Channels. 77 carbonate is laid down. So the cingulum of Trepostomes marks the senility of the race, and the Paleozoic Polyzoa fell a victim to the same disease as those Cretaceous forms which, owing to their calcareous skeletons, have been preserved to us to study. VIl.—Guacter Lake CHanneEts. By PERcY FRY KENDALL. (Concluded from the January Number, p. 29.) AVING shown that the ‘railway-cutting’ valleys of the Goathland area exhibit anomalies of position seemingly irrecon- cilable with the view supported by Professor Bonney that they are vestiges of an ancient river-system that has undergone readjustments -by the process of stream capture, I may now enforce the argument by exhibiting the contrast between the form and magnitude of the old and those of the new valleys in the same district. Sections across the Overflow Channels on Murk Mire Moor. (The datum in each case is 500 feet O.D.) The sections figured show the general relations of the two channels on Murk Mire Moor to the valley of the Murk Esk, but for a comparison of their respective magnitudes it would be necessary to extend the slope on the right hand down to a level below 200 feet. At the 500 feet contour the Murk Esk Valley is about three-quarters of a mile wide, and the area of the section below this level over a million square feet. At 725 feet, the level at which the upper channel was begun, the area of the section i is, roughly, 43 millions of square feet. If Professor Bonney’s explanation of the deserted channels be adopted it must be admitted that subaerial denudation had failed to obliterate or even to modify to any serious extent their 78 Professor Percy Kendall—Glacier Lake Channels, contours during the great lapse of time demanded for the excavation of the wide and very deep valley that is presumed to have usurped their functions. The preservation of the contours of these deserted trenches is, next to their anomalous relations to the relief, their most marked characteristic, and it has furnished the strongest argument yet advanced for the brevity of post-Glacial time. Whether excavated in granite, volcanic rock, slate, grit, sandstone, conglomerate, limestone, shale, or glacial materials, they show in a large proportion of cases scarcely any appreciable signs of weathering; the salient upper edges are only slightly guttered and the re-entrants at the foot of the ‘ batter’ only rarely are filled in by the running down of the banks. Exceptions to this rule are, however, not negligible, neither are they without significance. There are in Yorkshire, as is well known, several boulder-clays distinguishable by colour, superposition, and contents; they have, as I hope to show some day more fully, a geographical distribution of great interest: (1) the lowest, the Basement Clay, is not recognizable far from the coast, though representatives probably exist in many inland situations ; (2) the Purple Clay, represented in the country west of the Chalk Wolds of Lincolnshire by the Chalky Boulder-clay ; and (3) the Hessle Clay. The last appears to be limited to the seaboard of Yorkshire and the Vale of York, but an equivalent stage cf glaciation is recognizable in the valleys draining the eastern slopes of the Pennines from Swaledale to Airedale. A long interval marked by widespread and drastic denudation of the earlier deposits intervened between the Hessle stage and that which preceded it, and it seems probable that a great and general retreat and readvance of the ice took place in this interval. The maximum extension of the ice at the Hessle stage was many miles, and in some areas even scores of miles, short of that attained by the ice of the Chalky Boulder-clay, besides which, in the coast region the direction of its onset was different, the north to south component being preponderant, whereas at the earlier stage the impulse seems to have been directed more from the north-east. The limits of this readvance in Yorkshire can usually be traced with precision and clearness, in some places by well-defined moraines, in others by lake channels. The correlation of these two opposite classes of phenomena, the one an effect of deposition, the other of erosion, is comparatively easy—each forms the approximate boundary between a region in which the glacial deposits form an almost continuous mantle with the characteristic topographic features due to glaciation very fresh and complete, and areas in which the glacial deposits are reduced to a series of shreds and patches, often with long intervening spaces of driftless country. It is interesting to note that just as the Vale of York is spanned by the two great terminal moraines at York and Escrick respectively, so along the lower slopes of the Pennines two principal sets of channels trench the spurs between the river valleys. The upper set of channels is much shallower than the lower, whence it may be inferred that the extreme extension of the ice was rather ‘‘touch and go”’, and that a relatively Professor Percy Kendall—Glacier Lake Channels. 79 rapid shrinkage brought down to a condition of equilibrium that was maintained for a long period. The distribution and state of preservation of jake channels is interestingly related to the several drift sheets. Within the area occupied by the ice at the Hessle stage the channels are generally in a very perfect condition, all their contours are sharp and intact; outside this area, but still within the glaciated region, are traces of half obliterated channels such as those detected by Mr. Lower Carter in the valleys of the Don and Dearne. Finally, in the area that altogether escaped the ice invasion these anomalous valleys are, I believe, entirely absent, a fact that finds no explanation in Professor Bonney’s courageous hypothesis. The facts I have set forth appear to me to render it in a high degree improbable that the channels on Murk Mire Moor can be of any great antiquity—certainly not deserving even the qualified and indefinite reference to ‘‘ post-Jurassic, if not post-Cretaceous’’; and the fact that, like other ‘‘ certain channels”, of which I have seen many hundreds, they are not filled with, or even occupied by, glacial deposits, while the great adjacent valleys of the Esk and Murk Esk contain enormous accumulations of boulder-clay and glacial gravels, seems incompatible with their existence in pré-Glacial times. What- ever the agent that deposited the boulder-clay, whether, as I believe, it was moving land-ice, or whether, as Professor Bonney at one time thought, it was an ice-encumbered sea, it is hard to understand how channels far below the elevation reached by the Drift deposits in the neighbourhood could, if pre-existent, have escaped an infilling of glacial stuff. Mr. Bernard Smith has remarked that some channels are actually excavated in the drift deposits themselves, which seems decisive, for, to adapt an illustration of Hugh Miller’s, the graves cannot be older than the graveyard. I now return to an argument employed in the first portion of this - communication, namely, that based upon the systematic arrangement of the channels. Cleveland is only one of many districts in which channels of the same type have been detected. At the risk of prolixity I must mention several: the Pentlands and Lammermuirs(1)!; Cheviots (2); the Wansbeck and Coquet (3); Tyne, Wear, and Tees (4); the Cross Feil escarpment (5); Swaledale; Wensleydale; Nidderdale; Wharfedale, and Airedale (6); the Hambleton Hills; the lower slopes of the Pennines from Masham to Tadcaster (7); the basins of the Don and Dearne (8); the Yorkshire Wolds (9); the Lincolnshire Wolds (10); Black Combe (11); the Forest of Bowland, East * (1) Kendall & Bailey, Trans. Edin. Roy. Soce., vol. xlvi, pt. i, No. 1, 1908; (2) Kendall & Muff, Trans. Edin. Geol. Soc., vol. viii, 1903; (3) Smythe, Trans. Nat. Hist. Soc. Northumberland and Durham, N.s., vol. iii, pt. i, 1908; (4) Dwerryhouse, Q.J.G.S., vol. lviii, p. 572, 1902; (5) Kendall, Naturalist, 1912; (6) Jowett & Muff, Proc. Yorks. Geol. Soc., vol. xv, p. 193, 1904; (7) Kendall, Brit. Assoc. Rep., 1896; (8) Carter, Proc. Yorks. Geol. Soc., vol. xv, p. 411, 1905; (9) Kendall, ibid., p. 493; (10) Kendall and Carter, Proc. Geol. Assoc., vol. xix, p. 114; (11) Smith, Q.J.G.S., vol. lxviii, p. 402, 1912; (12) Jowett, Q.J.G.S., vol. lxx, p. 199, 1915. 80 Professor Percy Kendall—Glacier Lake Channels. Lancashire (12); the western edge of the Pennines from Rochdale to North Staffordshire, besides many districts in the North of Scotland. I have personally examined the great majority of these to the number of several hundreds of individual channels and on lines of country extending to much more than a thousand miles. When these are plotted upon or are compared with the maps wherewith various authors have illustrated their conclusions (deduced from other classes of facts) respecting the course of the old ice-sheets, it is found that with few exceptions.the channels are in the positions that would, upon such a theoretical basis, be assigned to channels draining lakes dammed up by the ice-margins. More than this, they exhibit a consistent fall towards the ice-free country. To regard this correspondence as merely fortuitous would surely be to rack ‘‘ the long arm of coincidence’’ to dislocation point. One may start from Edinburgh and follow an early continuous succession of channels (not, however, of the same period), all sloping in the line of route, almost to the Wash, and if, as I suspect, the through-valley at the common source of the Little Ouse and the Waveney at Lopham’s Ford, near Diss, be an overflow channel from the time when the Hessle Clay ice-front stood about Cromer, then the final release of the East Coast drainage must have been by the Straits of Dover. To such an orderly and consistent system of drainage I know in all the areas enumerated but one unexplained and at present unexplainable exception, namely, the channel at Moor Close Plantation, Robin Hood’s Bay. Itis a depression quite shallow and innocent-looking at the upper end, but rapidly deepening into an extremely fine gorge. By the irony of fate, not only did this escape my scrutiny when working over the Cleveland district, although I crossed its evanescent upper end several times, but, oddly enough, Professor Bonney’s itinerary indicates that he traversed its length, yet neither he nor I noticed that 2¢ slopes the wrong way and outfalls below the level of any possibly related system. I summarize the principal objections to Professor Bonney’s explanation of these remarkable channels as relics of a very ancient drainage system possibly antedating the Cretaceous period :— 1. Their restriction to the glaciated parts of our country. 2. Their ‘railway-cutting’ contours prove them to have been produced by large volumes of water. 3. The evidence of their production at a very recent epoch. 4. The way in which they traverse watersheds and their indifference to the geological structure of the country. 5. The continuity of the direction of their ‘ fall’ through wide tracts of country. 6. The discontinuity of the slope where wide gaps occur in the sequence. 7. The occurrence of aligned sequences along the face of escarp- ments and along both sides of a river valley. 8. The occurrence of many parallel channels trenching a single spur. 9. Their occurrence in glacial deposits, though this goes more against the date than the mode of formation. 10. The rarity of any infilling of boulder-clay. Reviews—Dr. J. W. Gregory’s Geology of To-day. 81 On the contrary hypothesis that these channels were produced by the outflowing waters of temporary lakes upheld by an ice-barrier, all these phenomena find an explanation, and the lakes themselves could in most cases have been predicted from the positions of the ice-margins that were deducible from other classes of evidence. I do not overlook the fact that there are two fundamentally antagonistic explanations of the ‘ Drift’ phenomena—the Land-ice theory and the ‘Great Submergence’, but whichever of these interpretations be the right one, neither is compatible with the ‘river-trespass’ hypothesis. On the other hand, I have long thought that the study of these ‘‘ certain channels’? did administer the merciful and much needed coup de grdce to the ‘Great Submergence’. REV Lew s- I1.—Groroey or T'o-pay: a popular introduction in simple language. — By J. W. Greeory, F.R.S., D.Sc. 8v0; 328 pp., 26 plates. London :.Seeley, Service & Co., Ltd., 1915. Price 5s. net. HIS is one of a series, ‘‘ The Science of To-day,” intended to be at once advanced and popular: advanced in the sense of being abreast of the latest facts and theories, popular as being intelligible to those unfamiliar with technical modes of expression. ‘‘ Geology,” as the author fully recognizes, is a big mouthful; ‘“‘a full digest of modern geology would be impossible in the space of a book of this size, and it would also be comparatively useless to a general reader.” This being so, 1t is surprising that the author or the editor, if there be such a person, should have weighted the subject by the inclusion of paleontology, by which we do not mean such account of ‘‘ The Age of Trilobites”’, ‘‘The Age of Graptolites’’, and so forth, as is contained in ‘‘ Part III, Historical Geology’’, but rather the more biological aspect of the science that is headed ‘‘The Story of Life on Earth” and constitutes Part IV. This could easily and naturally have been expanded to form an independent volume in the series, thus leaving space for the more adequate treatment of certain strictly geological questions, which in the book as it stands are discussed too briefly or not at all. For instance, the excellent chapter on the Age of the Earth contains no reference to that most fascinating method of investigation provided by pleochroic haloes; and, even in such historical _ geology as there is, one would have expected a reference to the remarkable Middle Cambrian fauna described by Walcott from British Columbia and supposed also to have been detected in our own Islands. Let it none the less be admitted that if, in ‘‘the round world and all that therein is”’, the author has shouldered too Atlantean a burden, he has none the less borne it right well. Professor Gregory is one of the very few geologists of the present day who has attempted, or at least attempted with any success,.to carry on the traditions of the heroic age. ‘l'o him the description of a new species of microscopic fossil comes as easily as the survey of an unexplored continent; the forces that fashion the globe are as familiar to his pen as those that determine the shape of a sea-urchin; from Eozoon to Eoliths nihil DECADE VI.—VOL. III.—NO. II. 6 82 Reviews—Dr. J. W. Gregory’s Geology of To-day. a se alienum putat. In serious research this spreading of one’s self is apt to make tne result rather thin, with holes too easily picked ; but in a work of the present kind comprehensive knowledge and broad views are all to the good. With this capacity Dr. Gregory combines many years’ experience of lecturing to all sorts and conditions of men, and the facile touch of the ready writer. There are authors who would have been more cautious and exact, others whose style would have lent greater distinction to a narrative deserving of the highest literary skill; but taken on the whole we doubt if any man living could have made a better job of it for the public, the publishers, and himself. A few improvements may be suggested. The relation of fiords and foldings to the rotation of the earth (p. 153) is expounded more securely than in the author’s recent book on the subject, but is far too condensed for the general intelligence. The statement on p. 307 that the sub-Crag implements prove the presence of pre-Glacial man in this country is not very easily reconciled with the conclusion (p. 817) that ‘‘the geological history of man is confined to the Pleistocene Period’, and that paleoliths are not likely to be found below the Boulder-clay; Dr. Gregory may be right in claiming that much of the Red Crag has been redeposited (‘‘ when” is another matter), but can he claim the whole of the Norwich Crag series as Pleistocene? Few, even amongst the most mechanistic of philosophers, will be found to agree that ‘‘ all the definitions of life and of vitality apply to the more complex forms of crystal growth” (p. 234); perhaps Dr. Gregory does not sufficiently realize that life is a property, not of a certain form of matter, but of an organism. If the wind that rounded the grains and cut the pebbles of the Torridon Sandstone was dry, its dryness may have been due to cold or to passage over an ice-field; we cannot ‘‘safely conclude that the North Atlantic was not then in existence” (p. 194). In Dinotherium it is not the canines but two incisors of the lower jaw that are bent downward (p. 279). On p. 192, Atikokamia, from a Lower Eozoic limestone in Canada, is accepted as a fossil, but there are respectable geologists who regard it as of inorganic origin. Dr. Gregory kindly gives the etymology of generic names: he may like to note that the Greek for a beast is Oyp, for moss (or mossy seaweed) Bpvov, =bryon not brion; that Megalania does not mean the big butcher, but is derived from j\ayw, 1 roam; that ‘‘bent-jaw” is Camptognathus, but that the name he wants is Compsognathus, meaning ‘‘ elegant jaw’. ‘‘Mont Pelée” is a false concord. The English grammar also has suffered, probably from too rapid proof-reading. The illustrations deserve a word of praise, but it should have been pointed out that the setting of Karl Hagenbeck’s reproductions of extinct saurians is, from the nature of the case, not so appropriate as the backgrounds which Miss A. B. Woodward has given to her ‘vigorous sketches of similar monsters. More reference might have been made in the text to some of the plates. The striking frontispiece —a statue of Agassiz pitched head-first through a stone pavement— will help to sell the book, but we can find no further reference to it and no explanation except that some-one or some-thing ‘“‘upped with Reviews—Dr. van Hoepen—Stegocephalia, Senekal. 88 his heels”. Does the public realize that in Californian, unlike Scottish, universities earthquakes are more usual than undergraduate Claes.) 2 One does not look to a book of this kind for original observations or ideas, and it is in fact difficult for a reviewer whose knowledge is less exhaustive than that of Professor Gregory to decide when an opinion is taken from elsewhere, or when it has just left the writer’s fertile brain. The comparison of the Old Red Sandstone to the shingle rivers of New Zealand (p. 204); the solution of the difficulty in correlating American, British, and Scandinavian glaciations by a bold denial of any synchronism at all (p. 281); the ‘‘ explanation of the simultaneous extinction of many different kinds of animals” as due to-a reduction in their rate of breeding ‘‘ by slight changes in climate and food-supply that occurred at periods of great geographic change’’ (p. 293): to select these ideas as novelties may be only to expose one’s lack of learning. Fortunately the knowledge of every man, even in his own science, is always less than his ignorance; so that the most learned geologist may well profit by a reading of this popular summary. II.—SrreocepHaria or Sunexat, O.F.S. By Dr. E. C. N. van Horpen, M.I. HE material described in this paper is of very great importance, because it represents the only satisfactorily preserved large rachitomous Stegocephalian of Upper Permian age yet found. Dr. van Hoepen’s excellent description is unfortunately marred by his unsatis- ‘factory illustrations. These are rather poor half-tone blocks of photographs and, as always, fail to show the really interesting structural details. Uyriodon senekalensis, as the form is called, is a large animal of a flattened body form, with short and rather feeble “limbs. The skull is only partially preserved, the important occipital region being largely missing. The exoccipital and basi-occipital appear to be extremely similar to those of Hryops, but it seems to the reviewer that the bone described as the basisphenoid is really only the posterior end of the parasphenoid, from which it is said to be indistinguishable. In Hryops the basisphenoid is a very spongy bone, whose lower and lateral surfaces are completely sheathed by the parasphenoid, which even forms a large part of the basipterygoid processes, the cores of which are, however, formed by the cartilage bone. In a Triassic type near Capztosarus, and apparently in that animal itself, the basisphenoid is only represented by a small very spongy ossification round the sella turcica, and the pterygoids unite by suture with the edge of the flat expansion of the back of the parasphenoid. Judging from the description and figure, Myriodon in this region is an exact intermediate between the Lower Permian Hryops and the Triassic forms. The description of the lower jaw corresponds with that which the reviewer arrived at when, through the kindness of Dr. v. Hoepen, he had an opportunity of examining it. At that time, before the real structure of the Stegocephalian mandible, as described by Professor 84 Reviews—Dr. van Hoepen—Stegocephalia, Senekal. Williston and Dr. Broom, was known, the reviewer was puzzled by certain appearances which it is now clear are probably to be explained by the presence of a post-splenial and a precoronoid. The reviewer now knows that a post-splenial is present in ‘ Bothriceps’ hualeyz, and that the large bone interpreted by him as the coronoid in Micropholis is really the same bone. It probably occurs also in Batrachiderpeton and ‘ Loxomma’, though the evidence here is not yet clear. The vertebral column is similar to that of Zryops, and the tail is fairly long. The shoulder-girdle has widely expanded clavicles and interclavicle, as in the large Triassic forms and in the small Permian Zrimerorachis and ‘ Bothriceps’ huwleyi. There is a cleithrum, which, as shown in the useful text-figure, caps the scapula as it does in Hryops. The scapulo-coracoid is structurally similar to that of Hryops, but the scapular portion is far shorter and makes a much more pronounced angle with the coracoidal end. The reviewer remembers seeing a suture between the precoracoid and the coracoid, and may perhaps mention here that he owes to the generosity of Professor Case a young scapula of an Eryopid which shows that the precoracoid was a separate bone forming part of the glenoid cavity, just as in Deinetrodon. The glenoid cavity has the peculiar screw shape common to primitive reptilia and Stegocephalia. The bones of the fore-limbs are generally similar to those of Eryops, but the author inclines to the belief that the humerus was much less twisted. The humerus of Mastodonsaurus, though other- wise similar to that of Hryops, is less twisted and may have resembled that of Dyriodon. There are stated to be only two ossified carpals and only four metacarpals; as this is a point of very great importance, and as Eryops and Cacops seem to have five fingers, it is desirable that a definite statement of the evidence should be published. The pelvis is generally similar to that of Hryops, the relation of the ilium to the sacral rib being the same in both: it is, however, perhaps still more similar to that of Mastodonsaurus when stripped of the addition of an ischium and a scapulo-coracoid with which it is provided in the familiar restoration. The hind-limb is similar to that of Hryops, so far as the latter is known, but it is very unfortunate that Dr. van Hoepen has not published a figure of the well-ossified and extremely interesting tarsus with five or six tarsals of which he gives a description. The reviewer some time ago suggested that the large Triassic Labyrinthodonts were derived from large Permian rachitomous forms, and these from the large Embolomerous amphibia of the Coal- measures; all subsequent work, both by other authors and by the writer, has tended to support this view: in particular the very interesting demonstration by Professor Williston that Zrimerorachis, which had been generally supposed to he the most primitive of the Texas amphibia, is really a specialized secondarily aquatic type, has removed a stumbling-block and added an important new idea. The writer regards Eryops as on the whole a neutral and perhaps in some ways a conservative animal. - Reviews—Dr. van Hoepen—Stegocephalia, Senekal. 85 In the reviewer's opinion the evolution in the large amphibia took the following course. ‘The amphibia were derived from unknown ‘Crossopterygian’ fish which, like all known members of that group, had a trunk of circular section and a somewhat depressed snout. The skull with the lower jaw formed a mass as high as wide .at the neck, asin Maw’s uncrushed ‘ Zoxvomma’ skull.. The body was long (more than twenty-nine presacrals in Pteroplax ?), and the tail probably even longer ( Pholidogaster and Cricotus). The animals, as shown by the grooves for lateral line organs on the skull, were mainly aquatic. In Lower Permian times, whilst retaining their round body, they became largely terrestrial (Hryops and especially Cacops and allies), the lateral line grooves becoming obscure or absent. Subsequently, for some cause of whose nature I can make no suggestion, the head and anterior part of the body began to become depressed, the process culminating in such extraordinarily flattened forms as Cyclotosaurus. Concurrently the animal became secondarily aquatic. Many changes in the skull are correlated with this depression ; of these the most important are: (1) The gradual dorso- ventral thinning of the basiscranii, which leads to the almost complete suppression of the basi-occipital and basisphenoid, to the replacement of the single basi-occipital condyle of the early forms by the paired exoccipital condyles of later types, a process in which many stages are now known, and to the gradual replacement of stout basipterygoid processes of the basisphenoid by thin but necessarily broader expansions of the parasphenoid. (2) The gradual expansion of the interpterygoid vacuities from small slits in the Carboniferous forms to the enormous openings in Cyclotosaurus. Not so obviously correlated with the depression of the skull is a gradual shortening of that part of the pterygoids and of the quadrates, squamosal, etc., connected with them, which lie behind their articulation with the basiscranii. This results in the exoccipital condyles forming the extreme posterior ‘points of the skull in many Triassic types. ‘The primitive Carboniferous amphibia had an embolomerous column in which the pleurocentra and intercentra are perforated discs of nearly equal size; reduction of the upper part of the intercentra and of the lower part of the pleurocentra leads easily to the rachitomous type found in Permian forms: still further reduction of the pleuro- centra with a concurrent strengthening of the intercentra leads to the stereospondylous column found in the Triassic animals (there is unsatisfactory evidence in the Stuttgart Museum suggesting the occurrence of small pleurocentra in Mastodonsaurus and DMetopo- saurus). The clavicles of the typical Carboniferous embolomerous Pteroplaz are flat plates with parallel anterior and posterior margins very like those of the fish Megalichthys. he interclavicle is a very small rhomboidal bone with a rudimentary posterior stern. In the more terrestrial Lower Permian types, e.g. Hryops and Cacops, the upper end of the clavicle is narrowed and affixed to the front edge of the scapula, separated from it, however, by the cleithrum, and the interclavicle becomes proportionately larger. In the Triassic forms, in correlation with the depressed form of the head and anterior part of the body and probably with the aquatic habits, the lower end of the 86 Revews—Dr. van Hoepen—Stegocephalia, Senekal. clavicle and the interclavicle become enormously expanded into the great bony plates so familiar in Metoposaurus and other types. The upper end of the clavicle, however, retains the slenderness and lack of ornament which it acquired in the Lower Permian terrestrial stage. Beyond a reduction in size necessitated by the flattened body the scapulo-coracoid remains essentially unchanged throughout the series of changes, and the fore-limb itself is only slightly altered, being smaller and more feebly ossified in later types. If Dr. v. Hoepen is correct the number of fingers is reduced to four and the humerus becomes less twisted. Except a slight weakening no change seems to take place in the hind-leg and its girdle. From the foregoing account it will be seen to how large an extent the evolutionary changes in the temnospondylous amphibia depend on two causes, the gradual flattening of the animal and its gradual return to an aquatic life. Study of the perfect materials in the Walker Museum, under Professor Williston’s charge, and in the American Museum, have considerably strengthened my belief in the close relation of Ceraterpeton, Batrachiderpeton, and Diplocaulus, animals whose ancestors have not been connected with the temnospondyl stock since very remote times. If these three creatures do really form a morphological family, then we have direct evidence that a similar flattening and return to the water have produced identical changes quite independently in two quite distinct amphibian stocks. In any case, even if the three animals mentioned above be not related, the resemblance in structural details between Deplocaulus and the Stereospondyls, which is very marked, must be due to convergent eyolution, because whilst Dzplocaulus is Basal Permian the stereo- spondyl structure did not arise till the Trias. The occurrence of four fingers in Myriodon whilst Eryops has five is another remarkable convergence to other amphibian stocks. We have thus direct and very strong evidence that two quite distinct groups of amphibia, separating very far back, have inde- pendently pursued similar evolutionary paths at quite different rates. We have seen that in both cases these changes can be referred back to a general flattening, and then the secondary adoption of an aquatic life. No trace of these trends can have been visible when the two lines separated, for, in one case at least, their origin must have followed the adoption of, and necessary adaptation to, a primarily terrestrial existence. This fact is only a particular case of a quite general feature of evolution, that allied stocks tend to pursue a similar course of change, the same and often striking new departures being initiated in diverse lines long after their separation, not necessarily at the same time or in the same order. Students of paleozoology have long been familiar with this fact, which is perhaps the most vital contri- bution to evolutionary data made of recent years, and it is interesting to see that botanists are now recognizing a similar ‘‘phyletie drift” in the subjects of their study, although zoologists and especially those whose work has dealt with the experimental study of evolutionary factors have so far paid little or no attention to it. M. H. Bergson’s philosophy, so far as it concerns biology, seems to depend on a super- ficial and incomplete appreciation of this great fact. Reviews—Economie Geology of Canada. 87 The importance of Myriodon lies in that it provides a useful intermediate stage between Zryops and the Triassic forms. D. M.S. Watson. I1].—Tan Economic Grotogy or CanaDa. IW\HE coal-fields of Manitoba, Saskatchewan, Alberta, and Eastern British Columbia are described in Memoir 53 of the Geological Survey of Canada, and those of British Columbia as a whole in a later memoir (No. 69), both by D. B. Dowling. The coal horizons range from Lower Tertiary to Cretaceous over the whole area covered by the two memoirs. In character the coals grade from lignite to true coal in undisturbed strata, and from coking coal to anthracite where the rocks have undergone considerable movement. In another memoir, No. 59, Coal Fields and Coal Resources of Canada, by D. B. Dowling, we learn that the great Dominion has by far the largest reserve of coal in the Empire, estimated at no less than 1,234,269 million tons; but most of it is lignite and brown coal, and is not available for commerce since it is as yet remote from profitable markets. Important supplies, however, occur on both the Atlantic and Pacific seaboards, and are able to compete with foreign fuel. The Canadian Department of Mines issues a publication on ‘Products and By-Products of Coal’’, by KH. Stansfield and F. E. Carter, which brings together in a compact and practical form useful information as to the methods of producing coke, gas, ammonia, and tar, from bituminous coal, and the properties and industrial uses of, these materials. The deplorable war conditions in Europe have made some of these products, especially coal-tar dyes, scarce in Canada; but while the demand in Canada is not sufficient to establish this industry on a profitable basis, it is shown that the production of certain other important by- -products of coal is peculiarly suitable for _ Canada, and the Dominion could be rendered less dependent on foreign sources of supply. ‘The results of the testing of six lignite samples from Alberta are given in a further publication of the ‘Department of Mines, by B. F. Haanel and J. Blizard, an instalment of an investigation of all the coals of Canada with a view to determining their best industrial uses. ‘he Albertan lignite isshown to be well adapted for utilization in the gas producer. Another interesting publication of the Department of Mines is a Report on the “‘Salt Deposits of Canada and the Salt Industry”’, by L. Heber Cole. The only salt deposits at present being exploited are those located in Ontario, which occur in the Salina formation (Silurian), but saline deposits are known to exist in Northern Manitoba and the Mackenzie basin of Alberta. These may be exploited as soon as these districts are opened up by railways, and may then supply the western provinces, which have now to pay high freight rates on their salt supply. The technology of salt manufacture is exhaustively described in the second part of the report. The clay and shale deposits of Quebec are dealt with in a preliminary report (Memoir 64, Geological Survey of Canada), by 88 Reviews—G. F. Becker—Isostasy and Radioactivity. J. Keele. Stratigraphically the clays now exploited range from the Pre-Cambrian to the Pleistocene ; but while there is a lack of high- grade clays like fireclays or pottery clays, there is an abundance of material suitable for the manufacture of rough clay products. The report contains valuable chapters on the origin and properties of clay, the effects of heat in clays, field examination and testing of the materials, and on methods of mining and manufacture, written mainly for the non-geological reader. Memoir No. 74 is ‘* A List of Canadian Mineral Occurrences’’, by R. A. A. Johnston. The bulk of the book is occupied with the names of the minerals arranged alphabetically, with notes as to their occurrence under the heading of each province. The second part gives the names of provinces and their divisions in alphabetical order, with the list of minerals found in each area appended. The work is an exhaustive compendium of Canadian mineralogy. IV.—Isostasy anp Rapioacriviry. By Grorex F. Becker. Bull. Geol. Soc. Am., vol. xxvi, pp. 171-204, March 31, 1915. FY\HE object of this paper is to draw attention to certain alleged discrepancies between recent developments in the theory of isostasy, and the age of the earth as determined by radio-active methods. Dr. Becker returns to his own method of calculating the age of a cooling earth, modified by taking into consideration radio-active supplies of heat energy. He assumes that the depth at which the temperature-gradient curve most nearly approaches the diabase curve ‘of fusion, i.e. the depth at which rock fusion is most easily - accomplished, is also the depth of Hayford’s level of isostatic compensation, 121 kilometres. Taking an earth with an initial temperature at the surface of 1,300°C., he finds the age to be 68 million years, radiothermal energy maintaining only one-seventh of the present temperature gradient. If radio-activity supplies two- thirds of the earth’s heat loss, then the age is 1,314 million years, and the depth at which fusion most readily occurs becomes 300 kilometres. Dr. Becker rejects such an earth as being probably incapable of volcanic phenomena. Professor Barrell (in the papers previously noticed in January last, p. 38) makes out a strong case for the existence of an astheno- sphere, extending perhaps to 600 kilometres below the level of isostatic compensation. He shows that the depth of easiest fusion must be below the level of compensation, and that it is to be looked for in the heart of the asthenosphere, that is, at a depth of about 400 kilometres. Combining this result with Becker’s analysis, the age of a cooling earth becomes considerably greater than 1,314 million years, and the proportion of the earth’s heat maintained by radio- activity becomes much nearer to its probable value—three-quarters, — or more (Grou. Mae., February and March, 1915). Geological deductions from isostasy and radio-activity are thus easily brought into harmony, and the source of the discrepancies alluded to by Dr. Becker are at least as likely to be found in his own interpretation of isostasy as in the simple method of determining the ages of radio- active minerals based on their lead-uranium ratios. ArrHur Hommes. Reviews— Whitman OCross—Lavas of Hawaii. 89 V.—Tue Kitonpixe anp YuKon GoLDFIELD. REPRINT from the Scottish Geological Magazine of a paper by Mr. H. M. Cadell on the Klondike and Yukon Goldfield in 1913 is included in the Smithsonian Report for 1914 (pp. 363-82). The paper-is both of scientific and of economic interest. The absence near Dawson of the signs of glaciation so conspicuous to the south is explained by the extreme dryness of the climate. But for the destructive work of glaciers in the Ice Age placer deposits of gold might have been found in Canada, Scotland, or Scandinavia. At the present time mining in the Klondike needs ample capital. The various ways employed for winning the gold—uincluding the remarkable dredging process, and the hydraulic or ‘ monitor’ method—are fully described and illustrated. About a million pounds worth of gold was extracted in 1913. The life of the field has been stated to be very limited, but there is likelihood of the discovery of paying reefs. ~ VI.—Txe Minerat Resources or THE Puinipprne Istanps FOR THE year 1914. Division of Mines, Bureau of Science, Manila, Philippine Islands, 1915. HE American administration of the Philippines has naturally led to a steadily increasing exploitation of the mineral wealth of the islands. Gold is by far the most important product, silver, iron, and lead following far behind. Deposits of copper, manganese, and coal have been worked from time to time, but have fallen into quiescence during recent years. Guano is now being mined as a fertilizer, and _ the War has reawakened interest in the manganese ores. A brief account is given of the occurrence of copper ores, associated with andesite, in Zambales. _ ViI.—Lavas or Hawatt and THEIR ReLations. By Warrman Cross. United States Geological Survey, Prof. Paper 88, 1915. HE author gives a full account of the petrography of the Hawaiian islands as far asthey are known at present. While the prevalent lavas are olivine basalts, many other types are represented, notably picrite basalt, bronzite basalt, trachydolerite, oligoclase-bearing lavas (e.g. kohalaite), soda-trachyte, nepheline basalt, and melilite basalt. This association indicates that the division of rock types into ‘ Atlantic’ and ‘Pacific’ facies is inappropriate, and further that alkalic and calcic magmas may be derivatives from a common source. The lavas of Tahiti, Samoa, and Réunion illustrate very similar associations. The author discusses various processes of differentiation. He declines to admit Daly’s view that the more basic lavas tend to issue from lower levels than the lighter ones, and denies that the association of alkaline rocks with limestones has any bearing on the origin of the former. Beyond indicating that periods of decreased activity were favourable to differentiation, and stating his opinion that the processes appear to have acted mainly on the liquid magma, the author advances no suggestions as to the physical mechanism concerned. 90 Reviews—Wabana Iron Ore of Newfowndland. VITI.—Wasawa Iron Orne or Newrounpranp. By A. O. Hayes. Canada, Geological Survey Memoir 78, 1915. N this beautifully illustrated memoir a detailed account of the I stratigraphy and petrology of the Lower Ordovician oolitic iron- ores of Wabana is placed on record. An unusually complete series of analyses has been made, confirming the petrographic identification of the chief minerals present—hzmatite, chamosite, and siderite. The writer concludes that the iron-ore occurs as a primary bedded deposit in a series consisting mainly of shales and sandstones. Pisolitic iron- ores have been found in the Llandeilo of Wales by W. G. Fearnsides, who, however, has urged their probable metasomatic origin. The writer gives a summary of the occurrences of other iron-ores of similar character, and notes the varying interpretations of their mode of origin, some authors favouring original precipitation, others holding the replacement theory. IX. Sxippaw.—In the Proceedings of the Liverpool Geological Society (xii (2), 1915), Mr. Jas. W. Dunn gives the results of many years work on Sheet No. 101 8.E. (Geol. Survey, 1 inch). He does not draw up any conclusions, so we must refer the reader to the paper for the petrology, with which it largely deals. REPORTS AND PROCHEHDIN GS. Liverroort GronocicaL Socrery. December 14, 1915.—J. H. Milton, Esq., F.G.S., F.L.S., President, in the Chair. The following paper was read :— ‘‘On the Igneous and Pyroclastic Rocks of the Berwyn Hills (North Wales).”’ By the late Thomas Henry Cope, F.G.S. Edited by Charles B. Travis. ; This paper represents the results of the work of the late T. H. Cope, F.G.S., during many years, supplemented by contributions by the editor. The area described, about 150 square miles in extent, includes portions of the counties of Denbigh, Merioneth, and Mont- ‘gomery. The sedimentary formations present range in age from the Llandeilo to Upper Tarannon and Llandovery, and have been subjected to cross-folding at two periods of time widely separated, giving rise to a periclinal dome which has been greatly denuded. The igneous and fragmental rocks, to which attention has been chiefly devoted, occur at various horizons in the Ordovician sediments, and comprise acid and intermediate lavas, intrusive sheets of inter- mediate and basic composition, and acid and intermediate fragmental deposits. ‘The most important pyroclastic rocks are three strongly marked bands of rhyolitic tuffs and agglomerates (‘‘ Peripheral Series”’), of Upper Bala age. They are traceable most clearly on the northern and western margins of the district, and correspond to the ‘‘ Ash Beds ”’ of the Geological Survey. In the southern portion Reports & Proceedings—Liverpool Geological Society. 91 of the area, near Llangynnog, in the Tanat Valley, four bands of spherulitic rhyolite occur, associated with acid tufts (‘‘ Lower Tuffs’’). They occupy a stratigraphic position at the base of the Bala series, and are correlated with the Snowdonian lavas of the Capel Curig — Dolwyddllen group. On the extreme easterly margin andesitic lavas and tuffs have been extruded from local vents, of which remnants are recognized. They comprise a series of hornblende-porphyrite, pyroxene, hornblende, and enstatite-andesites, with tuffs, breccias, and agglomerates of similar composition. These lavas represent the latest phase of eruptive activity in the Berwyn area on or above the horizon of the Bala Limestone, and they are probably related to the andesitic lavas and tufts of the Breidden Hills. The oldest volcanic rocks of the region lie in the centre of the Berwyn anticline, near Llanrhaidr yn Mochnant (the Craig y Glyn group). They are thin flows of spherulitic rhyolites, interbedded with calcareous acid tuffs, and are petrographically similar to the Llangynnog rhyolitic series, but of much greater age. They are associated with fossiliferous Llandeilo sediments, but it is considered that they may possibly be rather of Upper Arenig age. The intrusive intermediate series occurs only in the north-eastern and south-western corners of the district, in the valleys of Glyn- ceiriog and the Hirnant respectively. In the former locality the sill has been injected into Bala slates and grits, and overlies the middle tuff band. It isa hemicrystalline, vesicular rock, a keratophyre or soda-trachyte, composed of oligoclase-andesine felspar, pyroxene, and _ secondary products. The second type forms a series of five intrusive bands, hitherto mapped as voleanic ash, in the much faulted tract south of Llangynnog. These soda-rich rocks are hemicrystalline with an original glassy base, composed of oligoclase-andesine plagioclase and subordinate "pyroxene, now represented by pseudomorphs and interstitial chlorite. The structure varies from variolitic to insertal. The rocks resemble certain tholeiites, but do not correspond exactly with any rocks hitherto described, and have accordingly been provisionally termed «« Hirnantite”’. On the northern and westerly borders and in the central part of the district a number of basic intrusions form well-marked sills in the areas characterized by great dynamic pressure. They are well exposed in the following localities: Pen-y-bont (Llansaintffraid D.C.), Spring Hill (Pandy Glynn), Cwm Dwyll, Carnedd-y-ci (Llandrillo), Cader Berwyn and Llyn-llyn-caws, and Miltir-gerig. They are dolerites in various stages of preservation, frequently bearing analcite, and agree in many respects with the basic sills of Carnarvonshire. They are, however, exceptionally interesting by the evidence of albitization which they present, a process which has not hitherto been recorded for the rocks of North Wales. In one instance (Carnedd-y-ci) albite-dolerite is associated with quartz-keratophyre under circumstances which appear to suggest an example of a composite intrusion. 92 Correspondence—Dr. C. 8S. Du Riche Preller. CORRESPONDENCE. THE CARRARA MARBLE DISTRICT (APUAN ALPS). Srz,—In reply to Professor Bonney’s remarks on p. 47 of the Groroeicat Magazine of January, suffice it to point out (1) that the determination of the age of the crystalline schists and of the marble beds is essentially a question of paleontological and stratigraphical evidence, which, as I have shown, is absolutely conclusive, and is, more- over, universally accepted; (2) that it was neither the object nor within the available space of my paper to enter into the details of micro- scopical examination, the less so as this part of the subject has been exhaustively dealt with in the recent memoirs of Professor d’Achiardi, of Pisa, and of Mattirolo and Franchi of the Italian Geological Survey; (3) that the district of the Apuan Alpsis pre-eminently one which, owing to its extent and complexity, requires long and patient study of the entire area, and cannot be mastered by two admittedly incomplete visits, of only a few hours each, barely beyond one point of its periphery. C. Du Ricue Preiirr. EDINBURGH. January 12, 1916. THE CRYSTALLINE ROCKS OF THE PIEMONTESE ALPS. Srr,—In a footnote (p. 16) of my paper on the Permian formation of the Maritime and Western Alps in the Gxoxoeicat Macazrne of January, I mentioned that I propose to dealin a subsequent paper more fully with the crystalline schists and the pietre verdi areas, also in relation to the anti-Archzan and pro-Mesozoic views of Franchi as opposed to those of Zaccagna. In the meantime I should perhaps mention that in the most recent Italian geological maps just come to my notice the extensive crystalline cale-schist formation, which up to 1909 figured as pre-Paleozoic, has been rejuvenated to Mesozoic. C. Du Ricuz PRELLER. EDINBURGH. January 12, 1916. Si TAL OPN IS5 Sa 5 ARTHUR VAUGHAN, B.A. (Cant.), M.A. (Oxon.), D.Sc. (Lond.). BoRN MARCH, 1868. DIED DECEMBER 38, 1915. (WITH A PORTRAIT, PLATE V.) Tur death at the early age of 47 of Dr. Arthur Vaughan, which took place at Oxford on December 8, removes one of the most brilliant of British stratigraphical geologists. Dr. Vaughan was the son of the late William Vaughan, F.I.A., Actuary to the Board of Trade, and was born in London in 1868. After a highly successful career at University College School, he entered University College, London, in 1885, and there acquired his first interest in geology from the influence of Professor Bonney. In 1887 he entered Trinity College, Cambridge, with an open scholarship, Grou. Maa., 1916. PLATE V. ARTHUR VAUGHAN, B.A.(CantT.), M.A.(Oxon.), D.Sc.(Lonp.). 1868-1915 o Obituary—Dr. Arthur Vaughan. 93 and in his first year obtained a major mathematical scholarship. He was third Wrangler in [890, and in 1891 obtained a First Class in mathematical physics in Part II of the Mathematical Tripos. He also obtained Ist class Honours in Mathematics in the London B.Sc. examination. These academic successes, brilliant though they were, were not considered by his teachers to do full justice to his ability. On leaving Cambridge in 1891 he accepted a post as Senior Science Master at an Army coaching establishment at Clifton, and remained there till 1910. ~ His earliest papers were on mathematical physics and dealt with the earth’s crust, but shortly after settling at Clifton he became acquainted with "Edward Wilson, then the Curator of the Bristol Museum, and ‘to Wilson’s influence the definitely geological bent of Vaughan’s main work may in a great measure be attributed. Wilson was principally interested in the Jurassic rocks, and it was to these that Vaughan first turned his attention, his earliest geological paper, «The Lower Lias of Keynsham ”’ (1902), being written in collabora. tion with Mr. J. W. Tutcher. During the years 1900 and 1901 he was engaged in the study of the splendid series of sections exposed in constructing the South Wales direct line between Filton and Wootton Bassett. The strata exposed range from the Old Red Sandstone to the Kimmeridge Clay, and include a fine section of Carboniferous Limestone. It was the study of these latter rocks which induced Vaughan to re-examine the Avon section, and led to the work with which his name will always be associated. His paper on the Carboniferous Limestone of the Bristol Area, which was published in 1905, has already become a ' geological classic, and as regards the wide applicability of the results, _ and the stimulating effect upon other workers, it may confidently be ciaimed that no more important piece of paleontological stratigraphy -has been carried out since Lapworth’s work on the Lower Palzozoic rocks. . Vaughan’s results at once began to be applied by keen workers in numerous parts of the British Isles, and he himself described the Rush (1906) and Loughshinny (1908) sections in collaboration with Dr. Matley, and that of Gower (1911) with Mr. (now Lieutenant) EK. L. Dixon. The above papers are principally concerned with the zonal succession of the Lower Carboniferous rocks, but deal also with the mutations of Carboniferous Corals and Brachiopods, a subject in which Vaughan quickly became deeply interested. His views on the lines of development in the case of Corals are set forth in a paper on the Avonian of Burrington Combe (1911). | The rapid growth of interest in the Carboniferous Limestone led to many problems being submitted to him, and instead of spending his spare time in healthy field work he came to be more and more contined to indoor work, which was carried out under none too favourable conditions. He was a man who never spared himself, and it is to be feared that out of the kindness of his heart he undertook much identification with which he really ought never to have been troubled. The duties of an Army tutor are also of a very exacting character, and all this hard work began about 1908 seriously to affect his health. 94 Obituary—Dr. Arthur Vaughan. In 1905 he became Secretary of the British Association Committee for the investigation of life-zones in the British Carboniferous rocks, and drew up a series of important reports. Particular attention may be directed to those of Winnipeg (1909), Sheffield (1910), and Manchester (1915). In the Winnipeg report he correlated the Carboniferous Limestone (Avonian) succession in various parts of the British Isles, and threw much light on the phasal equivalents, while that at Manchester, his last piece of work, is concerned with the shifting of the western shore-line in England and Wales during the Avonian period. The Sheffield report (1910) correlates the British . and Belgian succession, and was the result of a visit paid to Belgium in the summer of 1909. Vaughan paid a second visit to Belgium in 1912, this time in company with a party of British geologists, and had the satisfaction of completing his Belgian work in a paper published in the Geological Society’s journal last year. The importance of this work was quickly recognized by Belgian geologists, and he was elected a Foreign Member of the Geological Society of Belgium. He received the Wollaston Fund from the Geological Society in 1907 and the Lyell Medal in 1910. In 1910 Vaughan moved to Oxford, having accepted a post as Lecturer on Geology in the University, and the charm of his personality and his marked ability as a teacher made him very popular with his students. While at Oxford his attention was particularly directed to questions bearing on the evolution of animal life, and breaking new ground he devoted much time to the study of fossil ungulates. He was also engaged on a textbook of paleontology written on somewhat novel lines, for the illustration of which Mr. Tutcher had prepared several hundred photographs. Although this is left unfinished, there is hope that it may prove possible to publish it. Though his lighter duties at Oxford caused some improvement in Vaughan’s health, it was still the cause of much anxiety to his friends. In 1914 he visited Australia with the British Association, and was able to satisfy himself that the remarkable Permo- Carboniferous strata were correctly correlated with the Artinskian of Russia, He hoped to have the opportunity of visiting Russia for the examination of these strata, and with his usual thoroughness occupied himself during the last years of his life with the study of Russian. _ Probably the characteristics which impressed themselves most on the many friends who mourn his early death were his geniality and loyalty, the courage with which he stuck to his work through long years of failing health, and the remarkable grip and clear-sighted logical analysis with which he tackled any problem. S. H. R. LIST OF PAPERS BY ARTHUR VAUGHAN. ‘‘ Stress within a Sphere due to inequalities at its surface, with application to the Harth ’’: 1897, privately printed, Taylor & Francis. ‘“* The Corrugation of the Earth’s Surface and Voleanic Phenomena’”’ : GEOL. MAG., Dec. IV, Vol. I, pp. 263-70, 1894. Obituary—Dr. Arthur Vaughan. 95 ‘Remarks on Mr. Mellard Reade’s Article ‘On the Results of Unsymmetrical Cooling and Redistribution of Temperature in a Shrinking Globe as applied to the Origin of Mountain Ranges’ ’’: ibid., p. 312. “Problems connected with a Cooling Earth ’’: ibid. , p. 505. “The Making of Mountains: A Reply to Mr. Mellard Reade’’ : ibid., Vol. II, pp. 93-6, 1895. ‘The Argument for Solidarity drawn from Ocean Tides’’: Proc. Bristol Nat. Soc., ser. II, vol. viii, pp. 269-73, 1899. “‘Notes on the Corals and Brachiopods obtained from the Avon Section and preserved in the Stoddart Collection’’: ibid., vol. x, pp. 90-134, pls. i-ii, 1903. “The Lowest Beds of the Lower Lias at Sedbury Cliff’’: Abs. Proc. Geol. Soc. 1902-3, p. 124; and Q.J.G.S., vol. lix, pp. 396-402, 1903. “The Paleontological Sequence in the Carboniferous Limestone of the Bristol Area’’: Abs. Proc. Geol. Soc. 1903-4, pp. 100-1, 1904; and Q.J.G.S., vol. xi, pp. 181-305, figs., pls. xxii-ix, 1904. ““Note on the Lower Culm of North Devon’’: GEOL. MAG., Dec. V, Vol. I, pp. 530-2, 1904. “* Note on the Brachiopods and Corals collected by Dr. Brendon Gubbin from the Carboniferous Limestone of South-West Gower, and the Zones which they indicate ’’: Proc. Bristol Nat. Soc., ser. Iv, vol. i, pp. 53-6, 1905. *“ The Carboniferous Limestone Series (Avonian) of the Avon Gorge ’’: Proc. Bristol Nat. Soc., ser. Iv, vol. i, pp. 74-168, figs., pls. i-xvi, 1906. Note on Corals in Report of the Committee on Life-Zones in the British Carboniferous Rocks: Rep. Brit. Assoc. 1906, pp. 309-11, 1907. ““A Note on Semimula’’: Ann. Mag. Nat. Hist., ser. VII, vol. xix, pp. 194-8, 1907. ‘**Note on the Coral-Zones of the eorian (Lower Carboniferous) ’?: Proc. Geol. Assoc., vol. xx, pp. 70-3, 1907. “A Note on the Carboniferous Sequence in the Neighbourhood of Pateley Bridge ’’: Proc. Yorks Geol. Soc., vol. xvi, pp. 75-83, 1907. “ Faunal Succession i in the Carboniferous Limestone (Avonian) of the British Isles’: Rep. Brit. Assoc., vol. Ixxviii, Dublin, 1908, pp. 267-9, 1909; vol. Ixxix, Winnipeg, 1909, pp. 187-91, 1 pl., 1910; vol. Ixxx, Sheffield, 1910, pp. 106-10, fig., 1911. “Note on Clisiophyllum ingletonense, sp. nov.’’?: Proc. Yorks Geol. Soc., N.S., vol. xvii, pp. 251-5, pl. xxxviii, 1912. ‘Correlation of Dinantian and Avonian’’: Q.J.G.S., vol. lxxi, pp. 1-52, pls. i-vii, 1915. “ The Reef Knolls of Clitheroe, Bowland, and Craven’? (read at the Yorkshire Geological Society, Leeds, June 24, 1915); to be published in the Proceedings of the Yorkshire Geol. Soc. now in the press. ** Shift of the Western Shore-line in England and Wales during the Avonian Period ’’ (read at the British Association Meeting, Manchester, 1915). With E. E.L.Drxon. ‘The Carboniferous Succession in Gower (Glamorgan- shire), with Notes on its Fauna and Conditions of Deposition’’: Abs. Proc. Geol. Soc. 1909-10, pp. 72-3, 1910; and Q.J.G.S., vol. Ilxvii, pp. 477-567, figs. [geol. map], pls. xxxviii—xl, 1911. With C. A. Matnry. ‘“‘ An Account of the Faunal Succession and Correlation [of the Carboniferous Rocks of Rush (Co. Dublin)]’’: Q.J.G.S., vol. lxii, pp. 295-322, pls. xxix—xxx, 1906. — “The Faunal Succession in the Carboniferous Limestone of the South-West of England and Ireland: Interim Report’’: GEoL. Mae., Dec. V, Vol. IV, pp. 466-8, 1906; and Rep. Brit. Assoc. Adv. Sci. 1906, York, pp. 292-3, 1907. —— .“‘The Carboniferous Rocks at Loughshinny (Co. Dublin)’’: Q.J.G.S., vol. lxiv, pp. 413-74, pls. xlix—l, 1908. With S. H. REyNotps. ‘‘On the Jurassic Strata cut through by the South Wales Direct Line between Filton and Wootton Bassett, Wilts’’: Abs. Proc. Geol. Soc. 1901-2, pp. 132-3, 1902; and Q.J.G.S., vol. lviii, pp. 719-52, figs., 1902. 96 Obituary—Dr. J. C. Moberg—W. R. Jones. With S. H. RrEynotps. ‘‘ The Rhetic Beds of the South Wales Direct Line”’ : ibid., 1903-5, pp. 41-2; and Q.J.G.S., vol. lx, pp. 194-213, figs., pl. xviii, 1904. — ‘‘Faunal and Lithological Sequence in the Carboniferous Limestone Series (Avonian) of Burrington Combe (Somerset)’’: ibid., 1910-11, pp. 94-5; and Q.J.G.S., vol. lxvii, pp. 342-92, figs. [plan], pls. xxviii- xxxi, 1911. With J. W. TutcHER. ‘‘ The Lower Lias of Keynsham’’: Proc. Bristol Nat. Soc., ser. III, vol. x, pp. 1-55, figs., 1903. With T. W. VauGHaNn. ‘‘ Notice of H. M. Bernard’s Work on the Poritid Corals (Recent and Fossil)’’: Science, N.S., vol. xxvi, pp. 373-8, 1907. With others. Excursion to Bristol: Proc. Geol. Assoc., vol. xx, pp. 150-6, pl. iv, 1907. — Report [as Secretary] of the Committee on the Faunal Succession in the Carboniferous Limestone of the South-West of England: Rep. Brit. Assoc., 1906-10. PROFESSOR, DR. J.C. MOBERG: Lund University, Sweden. We regret to learn of the death of Dr. Johan Christian Moberg, Professor of Geology at Lund University and Member of the K. Svenska Vetenskaps-Akademi, which took place at Lund on December 30, 1915. Professor Moberg was well known as a worker in the Paleozoic Geology and Paleontology of Sweden, especially of Scania, and produced a valuable summary of the subject for the use of the Geological Congress when it met at Stockholm. He was in his sixty-second year. WILLIAM RUPERT JONES. Born 1855. Di=D DECEMBER 17, 1915. Tue death is announced of the late Assistant Librarian to the Geological Society of London at the age of 60. Mr. William Rupert Jones was the son of the well-known geologist Professor Thomas Rupert Jones, F.R.S., for many years himself Assistant Secretary to the Society. He was appointed Assistant Librarian in 1872, and retired on pension in 1912, having served the Society for forty years. Mr. Jones acquired during his long service an extensive general knowledge of geological and other literature, and aided by a remark- able memory he was able rapidly to assist authors and inquirers to references in almost any line they chanced to pursue. For many years his Catalogue of Geological Literature, although confined to that received by the Society itself, was the standard book of reference, from its simplicity and general correctness. And there are many authors who had occasion to appreciate his skill in the production of coloured diagrams to illustrate their papers, a labour which grew up gradually but quite unofficially. Mr. Jones, who leaves no issue, was buried in Brompton Cemetery. Erratum.— In the Gzorosrcat Macazine for January, 1916, p. 39, 7th line from foot of page, for ‘repeated substances have taken place” read ‘repeated subsidences have taken place’’.—Ep. Gon. Mae. We Three Quarto Volumes of about 400 pages each, ‘small 4to, and an Atlas of 66 pages of maps ; in colours, 133 X 19%, bound in heavy paper cover. Price £5 5s. per set net. 7 THE COAL RESOURCES OF THE WORLD. An Inquiry made upon the initiative of THE EXECUTIVE COMMITTEE OF THE TWELFTH INTERNATIONAL GEOLOGICAL CONGRESS, CANADA, 1913, with the assistance of _ GEOLOGICAL SURVEYS AND COUN et ee OF DIFFERENT EDITED BY THE GEOLOGICAL SURVEY OF CANADA. “The preparation of the monograph involved a large amount of special investigation in several of the countries from which reports were submitted, and the three volumes with the atlas of beautifully executed maps will serve as a fitting companion volume to The Iron Resources of the World.’’—Natwre. este OF BOOKS OFFERED FOR SALE AT THE NET PRICES AFFIXED BY DULAU & CO., LTD., 37 SOHO SQUARE, LONDON, W. CRAIG (E.H.C.). Oil Finding: an Introduction to the Geological Study of Petroleum. 2nded. London, 1914. 8vo. pp. 208. Cloth. 8s. 6d. 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Sewed. £1 net. CLIMATIC CHANGES SINCE THE LAST ICE AGE. A Collection of Papers read before the Committee of the Eleventh International Geological Congress at Stockholm, 1910. DULAU & CO., Litd., 37 Soho Square, London, W. SSS ee eee THE GHOLOGICAL MAGAZINE NEWASERIES.) DECADE. Vi. VOLE, Ml. No. III.— MARCH, 1916. ORIGINAL ARTICLIEHS. EEO DOE I.—Nores ON NEW OR IMPERFECTLY KNOWN CHALK Potyzoas. By R. M. BRYDONE, F.G.S. (Continued from Decade VI, Vol. I, November, 1914, p. 483.) . PLATE VI. Mempranipora supacuminata, nov. (Pl. VI, Figs. 1, 2.) Zoarium unilaminate, always adherent. Zoecia separated by a distinct furrow, which passes into a deep crevice at the junction points, widely rounded below but tapering very considerably and almost to a point above, with areas of the same shape aud upright rounded side walls thickening considerably below, and often developing something of an internal front wall; average length of area -28mm., breadth -2mm., but marginal zoecia often run much larger. Owcia. No trace of any ocecium has been observed. Avicularia vicarious, humble examples of the ‘ Lesuewri-type’, as although strictly conformable in general structure they are only _a little larger than the surrounding zocecia; the node at which the very scanty front wall of the lower part splits into two is very inconspicuous, and the internal front wall of the upper part is relatively much wider than usual in proportion to the section of the _ area which it encloses. (I have always felt that it would be admissible to argue, on the species standing by itself, that these cells were not avicularia but ordinary zocecia with the addition of a wholly unroofed ocecial chamber; but I have never doubted myself that they were avicularia, and the recently discovered species which follows seems to put this beyond doubt.) This species is only known to me from the base of the zone of B. mucronata at Portsdown, where it is scarce but well distributed. ‘Mempranreora Stupianpensis, noy. (Pl. VI, Figs. 3, 4.) Zoartium unilaminate, adherent. Zoecia piriform in outline (there being a considerable expanse of flat front wall below the area), and separated only by sutures; areas practically circular, average diameter °28 mm., but occasionally much larger ones occur. Oecia globular, of the water-bottle type, the constriction at the neck being slight but quite distinct, with a concave free edge falling ‘somewhat back from the areal outline, small in proportion to the zocecia and with rather vague outlines, almost invariably present in the type-specimen. Beneath them the areal margin is low and very DECADE VI.—VOL. III.—NO. III. 7 98 hk. M. Brydone—New Chalk Polyzoa. thin, but maintains accurately the circular areal outline. This makes it impossible to confuse the base of the damaged ocecium with the internal front wall of an avicularium as the latter sets well back from the areal outline. Avicularva vicarious, resembling very closely those of IM. subacumi- nata, but a little larger in proportion to the zocecia and with the nodal points standing out conspicuously. I have only one specimen, from Studland, of this species; but specimens of any adherent Polyzoa are so exceedingly scarce in the Studland Chalk and the species throws such useful light on the preceding one that I have felt justified in disregarding the general objection to a species founded on a single specimen. MemBranrrora DEMIssA, noy. (Pl. VI, Fig. 5.) Syn. M. Britannica, var. demissa, Bryd., GEOL. MaGc., 1910, p. 77, Pl. VII, Fig. 6. I am convinced that I was wrong in ignoring the doubts I felt at the time and treating this form as a variety of JL Britannica. Subsequent experience shows clearly that the front wall habitually developed in IL, Britannica solely as a platform for the ocecium or avicularium of the preceding zocecium never approaches in size or systematic nature that of JL demissa, while the bold sub-triangular areas of If, demissa are also quite distinctive. The specimen which I now figure—from Studland, of all unlikely places—is practically the only one I possess which shows clearly and perfectly the very fragile ocecia. There are six perfect examples in the Figure. They are merely gentle and vaguely outlined swellings, with free edges. which are marked off by a faint constriction and coincide exactly with the normal areal outline, and they form a strong contrast to those of M. Britannica, which are very bold. J. demissa first appears in rare small forms in the base of the zone of B. mucronata, but is represented, by normal forms as soon as the higher Chalk of the Isle of Wight and Studland is reached. The same treatment should be accorded to the other form described at the same time as a variety (var. precursor) of M. Britannica, and this form must stand as a new species, I. precursor. It is now known to range down to the zone of MM. cor-testudinarium, and though upwards it ranges into the zone of B. mucronata, it does not appear to reach the Weybourne Chalk, and as UZ. Britannica does not appear to range down into the Weybourne Chalk, they never even meet. It would be interesting to know the exact range of | Reptoflustrella Meudonensis, D’Orb.,1 which looks like a relation of M. Britannica, though clearly distinguished by its avicularia. Mempranipora Woopwarot, Bryd.,? var. PINGUESCENS, nov. CBT Vil, ie N62) This adherent form, which I know only from Trimingham, deserves. a recognition which seems properly limited to varietal. The round- ness of its areas and ocecia, the slenderness and flatness of its. 1 Pal. Terr. Crét. Franc., vol. v, p. 572, pl. 731, figs. 19-21. ? GEOL. MAG., 1910, p. 258, Pl. XXI, Figs. 1-3. R. M. Brydone—New Chalk Polyzoa. 99 avicularia, and its general sleekness of appearance are points which effectively distinguish it from the typical and abundant free-growing form of the zones of A. quadratus and O. pilula, but are hardly of specific value, indicating rather a stage in the development of a single persistent form. To emphasize the range of evolution in this species J have added a figure of the form of the zone of If. cor-testudinarium, which is practically the earliest known. MemBRANIPORELLA PontIFERA, nov. (PI. VI, Fig. 8.) Zoarium unilaminate, adherent. Zoecia slightly pyriporiform; areas oval with flattened upper end, average length *35mm., breadth -2mm.; side walls broad and bearing about six pairs of stout imperforate tubercles; in three instances in the type-specimen the area is bridged between a pair of tubercles by a broad arched bar without any lateral connexion or even suggestion of it. Oecia only known from damaged specimens, apparently of globular type; at the point of attachment to the front wall they generally absorb part of the highest pair of tubercles. Avicularia small, interstitial, mandibular, with a slender transverse bar occasionally preserved quite perfect. The figured specimen is of course very imperfect, as it must be assumed that in a perfect specimen all or nearly all the pairs of tubercles would be connected by bars in every zocecium ; but it could only be by the merest chance that such a specimen would be secured, and no amount of waiting would guarantee it. ‘The species is an obvious warning against hasty diagnosis of forms that look like spiny Membranipore; but it is probably a safe rule, as the front wall elements of Membraniporella were presumably always fixed, that that genus is not in question when any of the tubercles are perforate and presumably bases of movable spines. The species occurs very rarely in the zone of UW. cor-testudinarium ’ in Hants and the zone of If. cor-anguinum at Gravesend. MeEMBRANIPORELLA oBscuraTa, nov. (PI. VI, Figs. 9, 10.) Zoarvum adherent, almost always more or less multilaminate. Zowcia very small, average length -4 mm., with heel shaped to horseshoe-shaped apertures (the outline depending a good deal on the amount of encroachment of avicularia), the lower lip of which is a straight thickened bar generally bearing a distinct median denticle ; the slightly arched front wall should be pierced by four or five pairs of radiating slits, as seen in Fig. 10, but it is only rarely that this structure can be detected, although the general aspect is so emphatically Cribrilinid that I never doubted that it would prove to belong to that family. Owcia. No trace observed. Avicularia small, probably mandibular, scattered in abundance along the interzocecial furrows, which they almost wholly obscure and often fill up to above the level of the zoccial front walls. This species appears to be confined absolutely to the zone of M. cor-testudinarium, in which it is fairly common in Sussex and occurs also in Hantsand Kent. Its general indistinctness is, of course, 100 ° H. L. Hawkins—On Lovenia forbesi partly due to its exceptional smallness and perhaps also in part to the relative intractability of the Chalk it inhabits, but it must also be due in part to secondary calcification. It is clearly one, and apparently the first, of the group which includes Jf. castrum,' Bryd., and 2. pustulosa,* Bryd. ., and which is otherwise, except for a very brief interval at the base of the zone of B. mucronata, strictly unilaminate. EXPLANATION OF PLATE VI. (All figures magnified 12 diams.) Fie. : 1, 2. Membranipora subacuminata. Zone of B. mucronata. Portsdown. 3. M. Studlandensis. Zone of B. mucronata. Studland. 4, M. Studlandensis. Another part of the same specimen showing broken ocecia. 5. M. demissa. Zone of B. mucronata. Studland. 6. M. Woodwardi, var. pinguescens. Trimingham. 7. M. Woodwardt. Zone of M. cor-testudinarium. Seaford. 8. Membraniporella pontifera. Zone of M. cor-anguinwm. Grea: 0. M. obscwrata. Zone of M. cor-testudinarium. Seaford. (To be continued.) at If.—A REMARKABLE SrRucrure in Lovenra FORBESI FROM TILE re Miocene or Avsrratta. By H HERBERT L. HAWKINS, M.Sc., F.G.S:, Geological Department, Univer College, Reading. URING the preparation and arrangement of a series of Lovenia forbest from the Australian Miocene (presented to the Geological Department by Professor F. J. Cole), a peculiar interambulaeral structure was displayed. ‘lwo of the specimens are severely weathered, with the result that their surfaces are smooth (except for the areole of the large tubercles), while the sutures are clearly outlined in dark brown across the pale background of the plates. In this way there is revealed the surprising fact that plate-crushing and resorption, of a type similar to that often found in Echinoid ambulacra, occur in four of the interambulacral areas. There is no corresponding develop- ment in the ambulacra. iy. As far as I am aware, this peculiar condition has not been described ‘previously in the species under notice, nor in any other Euechinoid, whether Regular or Irregular. Apart from its intrinsic interest, this apparently unique development throws much light upon the mechanism whereby the more usual ambulacral plate-crushing is produced. Hence a brief description of the specimens seems desirable ; and the description is followed by a discussion of the problem as solved by this new evidence. The following description is based solely on the two weathered specimens referred to above. They are registered in the Paleonto- logical Collection of University College, Reading, under the numbers 546 A and B. Their dimensions (in millimetres) are as follows :— Ant.-Post. Diam. Transverse Diam. Height. i Nash Ye ie Rtn EL 20:8 112-9 Jey 45 . 3 23:0 24-0 1. IL-2 1 GEon. Mag., 1909, p. 398, Pl. XXII, Figs. 4, 5. 2 GEOL. MAG., 1910, p. 488, Pl. XXXVI, Fig. 9. Grou. Maa., 1916. Prats VI. hk. M. Brydone phot. Bemrose & Sons Ltd., Collo. Chalk Polyzoa. oars > q ft) ey \ f ee ey» ’ ve from the Miocene of Australia. 101 It will be noticed that A is of a slightly different form from B, being smaller, but of greater proportional length and height. Specimen B is, in fact, rather broader and flatter than is usual for the species. On the evidence of size and tuberculation, it must be inferred that A (Text-fig. 1) is a somewhat younger individual than B (Text-fig. 2), although both specimens possess approximately the same number of plates in their tests. In both examples the ambital angle is very acute, and the adoral surface almost flat. In each of the four paired interambulacra (areas 1, 2, 3, and 4),' the adoral surface is entirely occupied by three plates—the unpaired plate at the peristome border, and two large multitubercular plates which make a kind of plastron. Of these large paired plates, those -in columns la and 46 are crossed by a faint curved suture, seeming to indicate that they are of dual origin. Lovén (Htudes) has inferred that one or both of these plates are often double in Spatangids, but seems not to have detectedasuture in them. Thereis the appearance of a similar suture across the corresponding plates in columns 2a and 35 in specimen B, but as this occurs in that individual only it requires confirmation, and is ignored in the numbering of the plates in the succeeding description and figures. In column la (Text-fig. 1) the plate next above the ambitus (plate 4) is narrow but complete. In column 14 there are two imperfect, lath-like plates intervening between the large ‘ plastronal’ plate (2) and the first tubercle-bearing plate of the adapical surface (5). Both of these imperfect plates take part in the interradial suture, but taper away towards the adradial suture, the adorally situated one being the shorter. As a result, plate 5 is in contact with plate 2 at the margin of ambulacrum II. In specimen B (Text-fig. 2) the condition in this column is precisely similar, but plate 3 is represented by a minute fragment extending for only a millimetre away from the interradial suture. In column 2a, in specimen A (Text-fig. 1), plate 3 is complete, but tapers towards the ambulacrum, and is reduced to a very narrow strip at the adradial suture. In specimen B (Text-fig. 2) the corresponding plate is imperfect, disappearing at a distance of about two millimetres from the ambulacral margin. In column 26 plate 3 is complete, its height being about half that of the succeeding plates in specimen A, and about a quarter that amount in specimen B. On: the other side of the test precisely symmetrical and similar conditions obtain. In area 5 there is nothing comparable in degree with this compression and reduction of the plates. From the foregoing description, and particularly from the figures, it will be seen that there is developed in the interambulacra of Lovenia forbest a structure closely analogous to plate-crushing as found in the ambulacra of most Regular and many Irregular Echinoids. The only difference in character is that, whereas in ambulacral crushing the plates are usually detached from the perradial suture, here they survive at the interradial suture and fail to reach the adradial. The plate-crushing, in so far as it produces plates homologous with demi-plates, is restricted to the two sets of interambulacral columns 1 Lovén’s notation is used throughout. 102 H. L. Hawkins—On Lovenia forbesi bordering upon ambulacra IJ and IV. This in itself may be regarded as a piece of confirmatory evidence for the association with an ambu- lacrum of the contiguous columns of the interambulacra, as urged by Jackson (Phylogeny). The crushing occurs, to some degree, in all four of the lateral interambulacra, and even in area 5 an appreciable reduction in the height of the plates can be detected. It affects most seriously those plates that are next above the enlarged subambital plates; and is most intense in specimen B, the older of the two. In o Its 3 Sues TEXT-FIG. 1.—Plan of the adoral and part of the adapical surfaces of specimen A of Lovenia forbesi. x about 24. The lettering and numbering of,areas and plates,is in accordance with the method employed in Lovén’s Htudes sur les Echinoidées. The ambitus is approximately coincident with the outer margins of the plates numbered 2. All ornament is omitted. such specialized forms as Zovenia, these plates (Nos. 2 or 2+ 3), together with the primordial unpaired plate, become set apart early in ontogeny for the purpose of building a strong, flat adoral surface. There is practically no resorption cf plates at the peristome; and, indeed, one might even regard the great increase in size of the adorally situated plates as constituting a ‘‘ negative resorption ”’, and possibly exerting pressure upwards. from the Miocene of Australia. 103 With these large plates stereotyped and immovable, a bar to downward movement on the part of the later formed plates is developed at or near the ambitus. It appears that in ZLovenra there is no interruption in the production of new coronal plates from the oculars (at least during a large portion of the growth: period of the individual), so that the lower (older) members of each column become jammed against the adapical margins of the large plates. This assumption TEXT-FIG. 2.—Specimen B of Lovenia forbes: for comparison with Fig. 1. It will be noticed that the two figures are identical exceptin proportions and the degree of reduetion of the interambulacral plates at the ambitus. receives strong support from the fact that in this species the greatest degree of compression of the plates occurs in the neighbourhood of areas IJ and IV. ‘The actual distance (measured on the curve) between the ocular plates and the adapical margins of the large adoral plates is less along those two areas than in any other part of the test, while the number of plates in each interambulacral column is the same over the whole test. Conversely, the distance from 104 H, L. Hawkins—On Lovenia forbes. oculars I and V to the ambitus in area 5 is greater than the corre- sponding measure in any other area, and here we find but a bare indication of compression in a small reduction in the height of a few plates. A table of these measurements in the two specimens described will emphasize this point. Number of plates in each iamb. column, 13. Distance (in mm.) from edge of ocular plates to ambitus— Radius II. Interradius 1. Interradius 5. ALA i 15-9 16-2 19-8 Bist ‘ 16-0 16-2 19-0 Average height (in mm.) of one iamb. plate in these positions— AME tee : 1-223 C 1-246 C 1-523 B } : 1-231 C 1-246 C 1-461 (C indicates development of plate-crushing.) In specimen B, where the distances are relatively shorter, but the normal plates actually larger, than in specimen A, the degree of plate compression is greater. In view of these conditions, it seems. impossible to resist the conclusion that simple mechanical pressure has been the prime cause of this unusual development. The growth of tubercles (to which Lambert would ascribe much influence in ambulacral plate-crushing) can have no effect in this case, for the scattered tubercles, though large for a Spatangid, are far removed from the margins of the plates and have ample room for extension. In comparing the development of plate-crushing in this aberrant case with the similar structures in the ambulacra of many other Kchinoids, the place at which the reduced plates occur becomes an important feature. It is demonstrably at the line of junction between the unchangeable and immovable adoral plates and the less specialized movable plates higher in the column; that is, the latter plates are crushed against the barrier. In the case of the ambulacra (and interambulacra) of the Cidaroids. there is nowhere any hindrance to the progress of the plates from apex to peristome, and no plate-crushing appears. In the other Regular Echinoids, and in the Holectypoida, the major part of the perignathic girdle is established on the ambulacral plates next to the peristome, and must, to exercise its function, remain there constantly and unchanged. At once plate-crushing appears (in the ambulacra), at the peristome margin first, extending farther up the area as specialization progresses. In Lehinocardium cordatum, as I have shown recently, an abnormal rate of plate-growth occurs in ambu- -lacrum III; but those plates of the area that are on or below the ambitus have already taken on the large, immobile character of the plates of a Spatangid adoral surface. The new plates thus crush against a barrier situated on the adapical surface, and the compound plates are restricted to the ‘petaloid’ region. In the closed petals of Clypeaster, Echinarachnius, and Laganum, a similar block occurs at the outer limit of the petal, and crushed plates make their appearance within the petals of fully-grown specimens. The case of Zovenia under notice is a further, and even more obvious, illustration of the theory of plate-crushing in Kchinoids. P.G.H. Boswell—Quantitative Methods in Stratigraphy. 105 that I have urged repeatedly; and the theory may be restated by way of a summary of the preceding paper. In Loventa forbest (or any other Echinoid), persistent development of new plates from the ocular margin causes a downward (orad) gliding of the columns. If no structure is developed to interfere with this procession, the older plates become gradually resorbed at the peristome margin, or all gradually and uniformly decrease in size as they increase innumbers. If, however, some special character is assumed by a series of plates in a column (whether ambulacral or interambulacral), and this character, for reasons of function, must be maintained in a definite position in the test (e.g. the large adoral plates of the interambulacra in Zovenia or the ambulacral processes of the perignathic girdle in a Diademoid), the oncoming plates of the column become congested against the barrier thus formed. Under such circumstances the plates become lessened in height and restricted in width, forming demi-plates, and often coalescing to form compound plates. Plate-crushing is first developed, both ontogenetically and phylogenetically, at the line of contact between the moving column and the barrier. The resulting structure may be adapted subsequently for special functions (e.g. phyllodes, ‘prehensile’ petals, or consolidation of the test fabric), but in its origin it is purely a mechanical outcome of the growth of the Echinoid test. II].—Tae AppricaTion oF PrrroLosicaL AND QUANTITATIVE MeErHops. To STRATIGRAPHY. By P. G. H. BosweELu, A.R.C.Se., D.I.C., F.G.S., Imperial College, London, S.W. I. Inrropuction. ()* account of the aid it has given, paleontology has been termed the handmaiden of stratigraphy, but up to the présent time petrology has not been called upon, so far as it might have been, to fulfil its appropriate duty towards the elucidation of the problems of stratigraphical geology and paleogeography. The lithology of sediments has been studied very largely in the field, but is still in its qualitative stage. Systematic quantitative work has hardly been attempted. Used in conjunction with paleontology the broad study has proved of great value in determining facies, and in yielding clues to the disposition of land and water and their relative changes in past geological times. The fragments contained in the coarser rocks, such as breccias, conglomerates, greywackes, grits, etc., have been used to some extent petrologically as giving an indication of direction and distance of source, but the finer detrital minerals of sands, clays, limestones, marls, etc., have not yet been adequately studied with the same view. Our ultimate aim must be the knowledge of the exact mineral composition of every sedimentary rock in the geological column. In such a way only can the economic resources of our sediments become familiar, the exact conditions of deposit known, and the lesser features of paleogeography realized. 106 P.G.H. Boswell—Quantitative Methods in Stratigraphy. II. Prrronogicat Meruops. The usual petrological methods of treating sediments by panning, and the use of heavy liquids, divide samples into two important and convenient crops of densities respectively above and below a mean of about 2°8. Of the liquids in common use, bromoform, when it can be obtained, appears to be most convenient. Operations with it are clean, and, what is of great importance when hundreds of samples are being examined, very rapid, the time taken in washing with benzene, and drying, being a minimum. Its mobility is a valuable asset, but has given rise to the objection that separations are rendered less complete on account of convection currents which are set up in it by slight differences in temperature. If necessary, care can be taken to avoid these, and in the writer’s experience separation is quite as good, if not better, than with the more viscous aqueous heavy solutions, where the process takes longer and the grains move less freely. The only real objection to the use of bromoform is its loss by evaporation during separation, and while the washings (in benzene) are being concentrated. ‘Theoretically, bromoform may be used over and over again without end, but practically there is a slow and steady loss. This may be obviated to some extent by the use of separating funnels stoppered at the top, but they are usually too small to accommodate a sufficiently large quantity of sediment, the sand, etc., tends to hang round the sides, and the subsequent washing is often troublesome. An ordinary funnel fitted with a glass stopper or a rubber tube and clip leaves little to be desired; but with bromoform a large surface of liquid is exposed to evaporation. The funnel may therefore be covered by a clock glass. Mercury potassium iodide is the most suitable of aqueous solutions, crystallizing out less rapidly and being less viscous than Klein’s solution (cadmium boro-tungstate). It is very poisonous and has a corrosive action upon the skin, but these objections are not serious with clean working, for the liquid need not be touched. It should, however, be kept from air, and in contact with alittle mercury. While not as convenient as bromoform, for it is less mobile, and necessitates washing with water, and consequent loss of time in washing and drying, it is the best substitute when that liquid is procurable with difficulty (as in 1914-15). It may be quickly prepared in the laboratory from mercuric and potassium iodides, and, like other aqueous solutions, may be used and recovered repeatedly without appreciable loss. For the further separation of the heavy crop ( > 2-8) methylene iodide, of density about 3°33, is very convenient. The sediment is washed with benzene and the separation is therefore rapid. Its expense is an objection, but small quantities only need be employed for the (usually small) heavy crops. The portion of density > 2°8 contains the heavy detrital minerals which are of greatest interest, beauty, and value from a strati- graphical point of view. Further separations may be made from this crop by electromagnetic and electrostatie methods, by the use of heavier liquids, and by hand-picking. Apart from the included rock-fragments and compound grains, sediments exhibit considerable variation in petrology. Most of the P.G. H. Boswell—Quantitative Methods in Stratigraphy. 107 constituent minerals are allogenic. In the authigenic group occur glauconite, hematite, limonite, marcasite, opal, chalcedony, and other forms of secondary silica, calcite, dolomite, gypsum, barytes, etc. The cementing materials of rocks come under this head, as do also those minerals such as limonite, anatase, leucoxene, secondary silica, micaceous aggregates, etc., when they result from the decomposition in situ of other minerals. It is not certain to what extent these secondary minerals are also detrital, for they may have been themselves derived as a result of previous decomposition of rocks. Anatase has been frequently observed growing upon, and at the expense of, ilmenite and leucoxene.! The opinion has been expressed that the tabular form is probably always authigenic, but that the pyramidal form may be allogenic. Among the few deposits known to the writer in which anatase is really plentiful in fairly large crystals (grains “3mm. diameter) is the Pliocene (?) sand of St. Keverne, near the Lizard, Cornwall. The sand is full of ilmenite (decomposing to leucoxene) derived from the Lizard gabbro, and there is little doubt that the blue tabular anatase is a secondary product from ilmenite. In the Yeovil sands ( Inferior Oolite) abundant yellow tablets of anatase accompany the yellow and red rutile which makes up a large part of the non-magnetic residue. Koenigsberger describes rutile pseudo- morphs after anatase in the Eastern Aar mass,? and the unexplained abundance of rutile in many sediments indicates that much work _ remains to be done upon these isomers. Glauconite may be detrital in certain cases. Dr. A. Morley Davies holds the view, with which the writer agrees, that the glauconite of some of the Mesozoic and Cainozoic deposits was derived from older - beds and was not formed at the same time as the sediment. In that ease redeposition probably took place under similar (i.e. reducing) conditions to those of its formation. Certainly much of the glauconite of deposits of all ages from Cambrian to Pliocene has no suggestion of foraminiferal character about the grains. Side by side with the mineral analyses of the deposits, mechanical analyses, obtained by elutriation, should also be made. A good classification is that suggested by Mr. T. Crook: gravel 10 to 1 mm., sand 1 to -1mm., silt (or very fine sand) ‘1 to -01mm., and mud less than -01 mm. diameter. The material is, for practical purposes, sifted to |mm., and the mud or true clay portion estimated by difference in the elutriation with the form of apparatus he recommends.* If necessary, intermediate grades can be estimated and inserted later in the tables, which are not invalidated if sufficient grades had not been estimated previously. In sands (e.g. for glass-making, ete.), it is often desirable to know the percentage weights of the portions of diameter > °5 mm. and < 1 mm. (coarse sand), > °25 mm. and < ‘5mm. (medium sand), and > -1 mm. and < :25 mm. (fine sand); these can be 1 J. B. Serivenor, Min. Mag., vol. xiii, p. 348, 1908; H. H. Thomas, Q.J.G.S., vol. Ixy, p. 232, 1909; W.R. Smellie, Trans. Geol. Soc. Glasgow, vol. xiv, p. 267, 1911-12. 2 Economic Geology, vol. vii, p. 697, etc., 1912. 3 Hatch & Rastall, Sedimentary Rocks (London, 1913); Appendix by T. Crook, p. 350. 108 P.G.H. Boswell—Quantitative Methods in Stratigraphy. obtained, if required, by treatment with circular-holed sieves, but separation below °5 mm. by sifting is hardly satisfactory. A more detailed classification, such as the following, has then been found useful, and may be carried out with adaptations of the Schoene apparatus. Diameter in mm. Fine gravel , : Shes Coarse sand : ; 4.) = fomands<" Medium sand . F . >:265and<-5 >} Sand grade. Fine sand . > Levande < 25 Superfine sand (or coarse silt) > 05 and <1 ie ae silt ( : : > 01 and < -05 geo Clay : : : A < O01 Mud grade. The mud grade may be divided, if desired, into portions of diameter greater and less than -005 mm. In sediments the portion of diameter between 1 mm. and ‘01 mm. is found to be most amenable to treatment for heavy residues; that over 1 mm. diameter frequently contains compound grains, and consists. of the lighter minerals, while that below -01 mm. diameter, being a mud grade, tends to clog the heavy liquids during separation. During deposition (as during elutriation—the reverse “process) the final velocities attained by small grains are dependent upon their surface areas (and therefore their diameters) and shape, rather than upon their densities. Nevertheless, as a result of greater density, it is found that the heavy detrital grains in any sediment often have an average diameter less than that of the lighter constituents. Minerals like mica, which have an excellent cleavage and therefore tend to occur in thin plates with a large flat surface, settle down slowly, and have, in spite of their greater density, a greater diameter than that of the accompanying quartz and felspar. Probably a constant ratio exists between the surface area (and also volume, for the thickness. probably varies with the diameter) and that of the other grains, both of light and heavy minerals. Asa result of measurement of material from various British sedimentary rocks, it is concluded that the volume of each muscovite grain is usually rather less than that of the average grain of quartz and felspar (perhaps about 80 per cent), but that the diameter of the flakes varies from two to four times that of the other heavy minerals. (The thickness of the mica flakes has been measured by focussing methods and birefringence.) The following are a few actual examples, selected from a large number :— Diameter in mm. Other heavy detrital Muscovite. minerals. Bunter pebble-bed, Devon (Dr. H. H. ag 5 2 to -3 Yeovil Sands F 25 -06 Lower Greensand, Hunstanton: : : : 6 25 Thanet Beds, Bramford F : : : 15 04 London Clay, Holbrook : : é : “2 -08 Claygate Beds : : : : : 15 -05 Boxstones (Crag) . : . 2 : : -5 to +6 2 Lenham Beds ‘ j , : : : “4 2 Elutriation methods depend upon the final velocities of subsidence P.G.H. Boswell— Quantitative Methods in Stratigraphy. 109 of quartz. It is clear that each grade obtained by elutriation will contain a proportion of heavy grains which from their diameter ought to belong to a smaller grade. If the percentage of material greater than 2°8 in density were a considerable one, the method of grading would be vitiated. Apart from the occasional cases where quantities of such authigenic minerals as limonite, pyrite, and pyrrhotite, etc., are introduced (and these may be extracted early in the operations), the heavy crop reaches only 4 per cent by weight in special cases. The average found by the writer after numerous separations of rocks of all ages is about ‘6 per cent. It is often, especially in coarser sands and sandstones, much less. Fine sands consisting largely of grains *2 to ‘05mm. diameter, such as many of the samples of Bagshot Sands, appear to yield the largest residue (up to 4 per cent).” The earliest systematic work in this country on heavy detrital minerals appears to have been carried out by Allan Dick, and he was fortunate in choosing for his work Bagshot Sand from Hampstead Heath, which yields a large crop. Sands of diameter 2 to ‘5mm. (e.g. Red Crag, etc.) yield a much smaller proportion of heavy minerals. Ili. Tue Possrprnitres anp Limrrations oF THE MerHops. A Imowledge of the mechanical analyses of all the British incoherent sediments is economically valuable as well as of con- siderable geological importance. Our resources are not at present accurately known, but soil-analysts, authorities on water-supply and filtration, brick and pottery manufacturers, glass manufacturers, and workers in various branches of the engineering trades, particularly in the foundries, agree upon the importance of the data. From the purely geological point of view, many interesting deductions can be made regarding conditions of deposit, velocity of rivers and currents, and direction of drainage. We need, however, much more experi- * mental work like that inaugurated in this country by Forbes, Sorby, and others, and carried on abroad, particularly in Germany and the United States,> in properly equipped laboratories. The experimental work is largely synthetic, and seeks to build up deposits under certain known conditions; the corresponding analytical work upon geological deposits has rather tended to lag behind the synthetic—a result not expected in petrology. When sufficient data have accumulated it should be possible to devise schemes for graphical representation of sedimentary rocks, similar to those in use for igneous rocks. Diagrams might be used upon maps, and being placed at certain points over an outcrop, yield at a glance information as to heteropic or isopic formations, lithological changes, presence of shore-lines, etc. But not only should deposits actually mapped at the surface be so treated. Specimens from wells, water- and trial-borings should be carefully preserved and subjected to analysis. It is a matter of ' R. H. Richards, Ore-Dressing, 1906, tables in Appendix. 2 Exclusive of such local sands, etc., such as those bordering the granite masses of Devon and Cornwall. These sands may be full of tourmaline, etc. ® See, for example, the recently published Professional Paper 86, U.S.G.S., ‘‘The Transportation of Débris by Running Water ’’ (G. K. Gilbert). 110 P.G.H. boswell—Quantitative Methods in Stratigraphy. great regret that tens of thousands of borings should have been made and so little of the material met with preserved. For mechanical analyses only 10 to 20 grams of the deposit are required, and for mineral analyses about a kilogram. It is to be hoped that this work will be developed in future. The drawing of sub-formational contour-lines has already proved of great value in water-supply questions, and in work upon concealed coalfields.' Combined with the isopachytes (lines joining points of equal thickness*) of super- imposed beds, these contour-lines yield valuable information as to the date and trend of folds and faults and the extension of deposits under- ground. But it is also necessary to know the lithological variations of the buried strata, and if contour-like grade-lines are also to be plotted upon maps, and compared with isopachytes and sub- formational contours, our basis of work on underground deposits must be quantitative. If from the graphical representation of sediments (preferably from curves) we can devise a scheme which represents by a number the average mechanical composition of a rock, we shall, by plotting these numbers referring to ‘ grades’ upon a map, and drawing ‘contour-lines’, possess a valuable method of indication, not only of thicknesses of beds (by isopachytes), and of the form of the surfaces of concealed beds (by contours referred to Ordnance datum), but also of changes in lithology, the proximity of axes of unrest, etc., in rocks now buried deeply. Such information cannot fail to be of considerable economical value, and its academic interest is as great. In questions of water-supply much time and money will be saved if the thicknesses and exact mechanical composition (and therefore the permeability and filtering value) of the various members of the overburden with respect to the water-bearing stratum are known.? Not only the mechanical composition, but the mineral constitution also, of each bed occurring in a boring, should be worked out. Evidence of unconformity between rock-series is thus accentuated and may be of value where fossil evidence is lacking or the relations of the beds obscure in the small core of the boring. It may be serviceable in certain areas, for example, to regard the change of mineral composition which usually exists, as the dividing line between the Permian and Triassic systems. The proximity of masses of crystalline rocks, of igneous bosses, etc., or even areas of ancient sediments forming old land-areas, may be revealed from borings as a result of the study of detrital minerals of the sediments bordering such land-areas. Additional information may be gained regarding 1 Since the above was written Professor W. G. Fearnsides has read a paper before the British Association upon the Underground Contours of the Barnsley Seam (GEOL. MAG., October, 1915, p. 465). See also ‘‘ The Use of Thickness Contours in the Valuation of Lenticular Coal Beds’’ (G. S. Rogers and C. E. Lesher) : Heon. Geology, vol. ix, p. 707, 1914. 2 Professor E. Hull used the term isodiametric (or isometric) lines, as those joining points of equal thickness of a formation before denudation had acted upon it. See Q.J.G.S., vol. xviii, p. 127, 1862. * C. S. Slichter, ‘‘ Motions of Underground Water’’?: Water Supply and Irrigation Papers, No. 62, U.S.G.S. Hazen’s ‘ Uniformity Coefficient’ obtained by sifting is not satisfactory, and is applicable only to coarse deposits. kt. M. Deeley—The Thames Valley Gravels. LE the position and extent of old shore-lines, and in the development of concealed coalfields, especially on outer ground where borings are as yet scarce, indications of the possible projection of pre-Carboniferous rock masses through the workable measures must be of great value. The information obtained by a petrological study of the sediments will thus be combined with that resulting from work on the mechanical composition, and with. the analysis of records of borings and their cartographical expression in the form of isopachyte systems and sub- surface contours. If the results obtained actually fall short of the above ideal, the method will still be justified. A few years ago Professor W. W. Watts wrote in his suggestive Presidential Address to the Geological Society (1911): ‘In order to obtain what Dr. Marr has called the ‘ geogram’ of a formation in its greatest perfection, we require to know the entire extent of its variations, not only along its outcrop, but in that part which is hidden from sight.’”? The whole of the section ought to be quoted, if space permitted, in this connexion. The methods of work detailed above help considerably towards the perfect conception of the ‘ geogram’ of a formation. (To be continued.) TV.—Tue Frovrio-cracta, Gravets or tHE THames VALLEY. By R. M. DEELEY, M.Inst.C.H., F.G.S. (Concluded from the February Number, p. 64.) T about 55 miles we reach the Hendon Lobe fan. At Dollis Hill the base of the fluvio-glacial beds lies at a height of about 200 feet, whilst their upper limit at Hendon is about 280 feet. On Finchley Hill to the north-east the Boulder-clay lies between the levels of 240 and 340 feet. This was a small lobe, and the fluvio-glacial fan may have sloped rapidly towards the fluvio-glacial gravels of the main stream. On the section, Fig. 2, the heights are shown without _ correction for slope towards the River Thames. Where the Lea and Roding Valleys join the Thames Valley, and to the east as far as Hornchurch, the ice reached the fluvio-glacial gravels of the Thames. West of Woodford, at 43 miles, gravel caps the watershed between the Lea and Roding. Here the height of the deposit varies from 200 to 210 feet. That the Boulder-clay should occur here as low as 80 feet above O.D. is very interesting, for it shows that, as at St. Albans, the fluvio-glacial gravels must have been piled against the ice face and buried its end in places. Indeed, as the lower Thames is reached the evidence favours the assumption that in pre-Chalky Boulder-clay time the valley was perhaps within about 80 feet of its present depth, and was subsequently filled with a deep mass of fluvio-glacial gravel, a view, as previously stated, held by Pocock. At Dartford Heath, 22 miles, the gravel is from 90 to 140 feet above O.D. The upper portion of this deposit locks like a schotter formed by braided streams ; but the lower portion is a clean current- bedded gravel and sand, such as an ordinary river might form. The fossiliferous gravel at Greenhithe and Swanscombe, like the Dartford Heath deposit, lies within the upper and lower limits of 112 R. M. Deeley—The Thames Valley Gravels. the fluvio-glacial gravels; but the exact relationship of the deposits to the fluvio-glacial gravels is uncertain. It is about 28 miles from the eastern edge of the Map, Pl. LV, Fig. 1. The gravel at High Halston, 18 miles, is a deposit which is from 100 to 200 feet high, and may belong to this series of gravels. ‘The highest outlier at the Telegraph Station, which is still more elevated, cannot belong to the series of gravels we are considering. Leigh, at 15 miles, shows gravel from about 150 to 160 feet Prera O-D.; “whilst the Southend ‘eravel is from 100 to 160 feet. From the neighbourhood of Southend the gravels run in the direction of Sales Point at the mouth of the Blackwater River. In this stretch the gravel of the main stream seems to have been joined by a fluvio- glacial fan coming from the direction of Billericay, where it is from 220 to 240 feet above O.D. — Its distance from the fluvio-glacial gravel of the old Thames is about 16 miles, and allowing 5 feet per mile fall we get 14) to 160 feet as the height of the gravel of the main stream. Southminster stands on an outlier of gravel which varies from 50 to 80 feet above O.D., and this place is opposite the point where the centre line of the old Thames Valley reaches the east side of the Map, Pl. IV, Fig. 1. All the gravels of the Tilehurst Terrace do not contain erratics derived from the glacial drifts: On the south side of the River Thames Bunter pebbles are absent, except towards the east. Portions of the gravel to the south and west were formed by the local drainage, whereas the portions to the north side of the river were largely formed by the drainage from the ice margin, the deposit becoming a more and more mixed one as it is followed to the east. The slope of the Tilehurst Terrace deposits from the Goring Gap to the east does not appear to have been by any means a regular one ; but whether the irregularity is wholly due to the varying amount of water and sediment coming down from the various ice lobes or to the subsequent warping of the district is not clear. Perhaps the debris was poured into the Thames Valley by the St. Albans Ice Lobe in such quantities that it collected here in unusual thickness in the neighbourhood of the confluence of the Colne and Thames. At Southend the High-level Terrace Gravels wrap the slopes. in avery peculiar manner. Indeed, it would appear that the present estuarine portion of the Thames ‘Valley in pre-Chalky Boulder-clay time continued to slope to lower levels in a north-easterly direction, and that in Chalky Boulder-clay time the valley was deeply filled with fluvio-glacial gravels which have since been re-excavated, leaving traces of the High-level Gravel Terrace deposits at all heights from sea-level up to 130 feet or more. This filling up of the valley with glacial detritus in its lower reaches may have been due to the ereat quantities of material thrown into the valley by the Lea Valley Lobe and the ice lobes which debouched into the valley from the rivers of Suffolk and. Essex. During the time the Chalky Boulder-clay was being laid down the Tertiary and Cretaceous rocks extended some distance in a north- easterly direction into the North Sea, being probably continuous with those of France. Since this time subaerial denudation and coast R. M. Deeley—The Thames Valley Gravels. = 1138 erosion have removed this easterly watershed of the Thames and given it its present direction of outlet to the sea. Probably the initiation of the Straits of Dover dates from the advent of the first ice-sheet which crossed the North Sea to Britain, and if the Straits existed in Chalky Boulder-clay time they were probably very narrow. Indeed, the reason why the early ice-sheets of the Pleistocene period . were able to cross the North Sea was the absence there of the volumes of warm water which now pass from the south through the Straits. The erratics in the raised beach of the south coast of England probably reached their present positions at a later period; for there is much evidence which favours the view that the last cold period occurred long after the Tilehurst Terrace Gravels were laid down. It may be that the Tilehurst fluvio-glacial aeatels did not at any one time quite fill the valley between the heights shown by the line BB and CC, Fig. 2; but rather that terraces of very considerable thickness were formed between these limits, for the grading and aggrading of the valley varied in accordance with the varying quantities of material thrown into it from time to time by the glacier streams. Some of the gravels which stand at a higher level than those of the High Terrace remain to be noticed. Monckton } describes some gravels which rest on the Ashley and Bowsey Hills. He considers that some of the pebbles found in them point to a glacial origin. Mr. White found a pebble of grey chert with casts of detached joints of erinoids at Bowsey Hill and another of similar character at Ashley Hill. Both the black and grey cherts found may well have been derived from the Carboniferous Series to the north. These gravels also contain a great abundance of white quartz pebbles. On the north side of the Thames, opposite the Bowsey and Ashley Hills, there are also gravels at a similar height, and as shown on the Map, Fig. 1, higher-level gravels run along the south-eastern slopes of the Chiltern Hills, above the fluvio-glacial deposits of the St. Albans Ice Lobe. They also form a well-marked terrace resting on a platform about 400 feet high in the Kennet Valley and on the high land to the north-west of Bagshot. Here, however, they do not contain Northern Drift. Their extent and boundaries are very uncertain and the method of their formation is obscure. The Bowsey and Ashley Hill gravels. are shown thus + in the diagram, Fig. 2. They seem to be - much too high to have been formed when the St. Albans Ice Lobe was in existence. Some of the plateau gravels lower down the Thames may also be of the age of the Higher Terrace Gravels. A possible explanation of the existence of such high-level gravels containing Northern Drift erratics may be as follows The position of the Thames Basin is a very interesting one from the point of view of stratigraphical glacialogy ; for its southern, central, south-western, and western portions were outside the area occupied by the ice-sheet which advanced to some extent over the northern and north-eastern watershed ; and owing to its position on the edge of the ice-sheet, it felt the full effect of any variations in the position of the ice margin. 1 Q.J.G.S., vol. xlix, p. 314, 1893. DECADE VI.—VOL. III.—NO. III. 8 114 Rh. M. Deeley—The Thames Valley Gravels. Before we can consider the question of the high-level gravels of the Thames Valley as being in any way properly dealt with, it is necessary to get as clear a view as possible of the movements of the ice-sheets which invaded this area. This is a difficult matter to accomplish, for British geologists have generally confined themselves to considering the greatest area which can be shown to have been covered by ice and the directions in which it probably travelled ; but. the trend of the rock striz and the variable nature of the deposits in some areas show that the direction of the flow changed very con- siderably from time to time, as also did the areas covered by the ice at different times during what seems to have been the same epoch of glaciation. One of the most interesting ice-flows is that which passed over the Stainmoor Pass and carried with it the well-known Shap granite. That at one time this ice-flow passed in an easterly direction out into the North Sea is shown by the occurrence of this rock at Elwick, as far north as Hartlepool. This uninterrupted movement of the Stainmoor ice to the east was also shared by that coming through the Tyne Gap.’ Trechmann shows that the ice from Scandinavia pressed against the English coast between these two lobes. Subsequently the ice from the Cheviots was deflected in a southerly direction by this North Sea ice and passed down the coast. It has generally been considered that this deflection of the British ice-flows was only due to the advancing Scandinavian ice, but it may have been partly due to the waning of the British ice-sheets as the Scandinavian ice advanced and thickened. Lamplugh*? shows that further south at Flamborough Head similar changes in the direction of the flow took place, the Basement. Clay of Holderness being the oldest and having a Scandinavian origin, whilst the subsequent flow was down the coast. This alteration in the direction of the ice-flow becomes more marked as we reach Central and Western England. In the Trent Valley this change in the direction of ice-flow is very pronounced. Deeley * has shown that in this area the ice first came from the west, and that its fluvio-glacial gravels and sands went as far east as Grantham. Subsequently this ice-flow melted away and its place was taken by the ‘‘ Northern ”’ ice-flow which laid down the Chalky Boulder-clay. One lobe of this. flow turned towards the west and passed up the Trent Valley, laying down upon the older boulder-clays and fluvio-glacial deposits the Chalky Boulder-clay and its fluvio-glacial deposits. The ice from the west and that which came down the Derwent Valley advanced into a submerged country, a submergence probably due to the presence of the Scandinavian and Scotch ice in the North Sea. Associated with the hard till with glaciated boulders formed by the early western and Pennine ice, are clean current-bedded sands and eravels not containing flints, and sedimentary clays containing well- glaciated boulders, but no flint. That this ice-sheet was very thick in the Irish Sea is shown by the 1 Q.J.G.S., vol. lxxi, pp. 538-80, 1915. 2 Q.J.G.S., vol. xlvii, pp. 384-429, 1891. 3 Q.J.G.S., vol. xlii, pp. 437-79, 1886. R. M. Deeley—The Thames Valley Gravels. 115 fact that one lobe of it passed over the gap in the Pennines near Buxton and distributed Scotch and Cumberland rocks on the high land above Tideswell. At Bakewell, well up the Derwent Valley, there is a good deposit of boulder-clay formed by this ice. The graye-yard stands on it, and heaps of foreign erratics ure to be seen there. Another thick deposit of it is to be seen at Crich, where it rests upon a well-glaciated floor of Carboniferous Limestone. So thick was this ice in the Irish Sea, that it completely submerged Snaefell in the Isle of Man, which is 2,034 feet high. Coming from Cumberland and Scotland one lobe of it passed to the east of Wales into the Severn Valley. Here, reinforced by ice from Wales, it pressed against the Cotswold Hills, forming gravels and leaving Northern: Drift pebbles on their flanks, such as Millstone Grits and quartzite pebbles, but no flints. Such pebblesand gravels have been found, according to Lucy,’ at heights of 750 feet above the sea-level. If the ice reached such a thickness there must have been an overflow of water into the Thames Valley through the Andoversford Gap to the east of Cheltenham. Such thick ice would also pass over the Thames watershed into the Evenlode and Cherwell Valleys, and in this way Northern Drift found its way into the upper Thames Valley, where it is now found at heights considerably above the Tilehurst Terrace Gravels. As far as the British ice is concerned this would appear to have been the time of its greatest extension. However, the succession of events which preceded the advent of the Chalky Boulder-clay ice may have been much more complex than is here indicated. There is very little evidence of this in the area we are considering; but in Norfolk, Suffolk, and Northern Essex the complexity of the Drifts is very striking. Upon the westerly drifts of the Trent Basin there rest the Great Chalky Boulder-clay and its associated gravels and sands. It is clear from the arrangement of the deposits that, before the North Sea ice ‘advanced up the Trent Valley, the Irish Sea ice had retreated a considerable distance. Whether in the Trent Valley to the west of Burton-on-Trent the eastern ice coalesced with that coming from the west is uncertain. Lucystates that along the flanks of the Cotswolds, and running up to the Marlstone Terrace to heights of about 610 feet, there is a line of gravel containing an abundance of chalk flints. Therefore, although the British ice may have been reinforced at this time by the ice which formed the Chalky Boulder-clay, its gravels only reach heights of 610 feet, whereas the earlier British ice formed gravels at heights of 750 feet. That the Chalky Boulder-clay glacier reached the upper.end of the Evenlode Valley is clear; for Lucy states that at Paxford, 34 miles north-west of Moreton-in-the-Marsh, he saw in a field which was being drained fully five feet of boulder-clay, containing some flints, quartzose pebbles, Lias, greenstone, Millstone Grit, and syenite from Charnwood. At Little Wolford, about 8 miles east of Moreton-in-the- Marsh, in a gravel-pit, were found pebbles of a hard red species of chalk which occurs not infrequently in the Wolds of Yorkshire and 1 The gravels of the Severn, Avon, and Eyenlode, and their extension on the Cotswold Hills. 116 R. M. Deeley—The Thames Valley Gravels. Lincolnshire. Buckland, many years before, had recognized this red chalk. Another lobe of the Chalky Boulder-clay glacier moved up the Ouse Valley and reached the limits shown in the Map, Fig. lL. If the above reading of the teaching of the boulder-clays, sands, and gravels be correct, then the first erratics to reach the Thames Basin were brought into the district by the British ice-sheet which reached the more northern and western portions of the Thames Basin, but may not have reached the Ouse Valley or the Lower Thames Valley. It has been maintained by Tutkowski’ and others that near the margins of great ice-sheets cold and dry conditions prevail. Outside this dry area the climate, although cold, is much more moist, and the precipitation very considerable. It may be that some of the moisture which does not fall near the ice margin is precipitated on the ice some distance from its edge owing to local winds. To some extent this reduced precipitation at the ice margin is a feature of the Antarctic Continent, for Bouvet Island, although small and out in the open ocean, is completely covered with ice down to the water’s edge, whereas the coast of the continent, hundreds of miles to the south, is not ice mantled to the same extent. It is possible that Great Britain, before the Scandinavian ice first reached it, was outside the dry zone and, like Bouvet Island, snifered intense glaciation, but that as the Scandinavian ice advanced over the North Sea floor towards Britain the dry zone advanced with it, and that when the continental ice-sheet reached our shores the air had become so dry that the local British ice-sheet, partly or wholly, melted away. ‘That such a dry period existed is shown by the discovery of dreikanters* in the Midland Counties. _ As far as can be made out, all the boulder-clays we have considered seem to belong to one cold period,® but this is by no means certain. It may be that the Bowsey and Ashley Hill gravels and some others to the north-east along the edge of the Chiltern Hills, in the Kennet Valley, and to the north-west of Bagshot, may have been formed by the early outflow water of the British ice-sheet ; but that the Thames, as suggested by Sherlock and Noble,‘ then ran past St. Albans in a north-easterly direction scarcely seems probable, nor is it likely that it passed into the Ouse Valley near Buckingham, as suggested by Harmer. Sherlock & Noble® also suggest that the Clay-with-Flints is a glacial deposit, ie. a boulder-clay. Now, according to the evidence we have, the Clay-with-Flints occurs on those portions of the Chalk escarpment which was never overridden by the Chalky Boulder-clay ice-sheet, and does not occur on those portions which have been overridden. There is a marked difference between the Chalk escarp- ment to the south-west of Luton as compared with that to the north- east. Sherlock & Noble remark that ‘‘an ice-sheet coming from the 1 Scot. Geol. Mag., March, 1900. 2 Matley, Q.J.G.S., vol. Ixviii, p. 293, 1912. 3 Q.J.G.S., vol. xlii, pp. 439 and 466, 1886. 4 Q.J.G.S., vol. lxviii, p. 206, 1912. ® Tbid., p. 199. R. M. Deeley—The Thames Valley Gravels. EG north and north-west would sweep up these materials and produce a confused mass known as Clay-with-Flints”. But from the distribution of the boulder-clay and gravels the ice appears to have come from the north-east. Deep snow on the Chilterns may have modified the deposit. The Clay-with-Flints seems to be such a deposit as we may expect to find filling up surface channels formed by the subsidence of the chalk into underground channels resulting from the solvent action of water, or filling swallow-holes. As the Tertiary beds were removed they would supply material to fill up such hollows as they formed. The brick-earths thus produced rest upon a layer of clay and flints which seems to be a chalk residue. Sarsen-stones were once very probably distributed over the whole area, and where they rested upon the surface they were removed for building purposes centuries ago, or destroyed by atmospheric agencies. They are now only to be found where they were buried. At Sonning, Smith & Dewey’ give the height of the Boyn Terrace as 180 feet, and with this deposit they correlate the Dartford and Swanscombe Terraces. As the Tilehurst Terrace is at a height of 275 feet at Sonning, the Boyn Terrace? is thus 95 feet lower. Both at Dartford and Swanscombe the gravels lie well within the limits of the Tilehurst Terrace Gravels. They must, therefore, have been formed either before the Tilehurst Gravels were laid down or whilst the River Thames was re-excavating its valley through the fluvio- glacial deposits. Very few remains have been found in gravels on a level with the Tilehurst Terrace Gravels except to the south of the Thames on the east and west sides of the Darent River. Here at Dartford and Swanscombe mammalian and other remains have been found in considerable numbers. Much further work will have to be done before the age of these mammaliferous gravels can be said to have been settled. The remains they contain seem to show that there is a wide gap between them and the Taplow or Middle Terrace deposits. On this point Hinton® says, ‘‘ Excepting the elephant, rhinoceros, Felis, and possibly two of the deer, all the forms mentioned. differ from those whose remains are found in the earliest deposits of the next or Middle Terrace of the Thames Valley at Grays, and they approach those occurring in the ‘ Forest Bed’ series and the Upper Val d’Arno Pliocene.” It is possible that the Dartford and Swanscombe Gravels are in part, at least, older than the fluvio-glacial gravels, for Leach * found in the lower portion of the Dartford Heath Gravel mammalian remains of beasts which it is unlikely lived when the upper portion of the gravel bed was deposited by a river fed by streams coming from an adjacent ice margin. 1} Arche@ologia, vol. xiv, p. 178. 2 The Geology of the Country around Windsor and Chertsey (Mem. Geol. Surv.), p. 67. 3 Proc. Geol. Assoc., vol. xxi, p. 492, 1909-10. 4 Proc. Geol. Assoc., vol. xxiv, p. 340. 118 F. R. C. Reed—On the genus Trinucleus. V.—Sepewicx Museum Nores. Nores on tHE GENUS Z'RrINUCLEUS. Part LY. By F. R. Cowper REED, Sc.D., F.G.S. Tur Gunat AREAS. (J\HE triangular non-perforated areas lying on each side of the glabella and bounded in front and laterally by the fringe are usually described as the cheeks and distinct from the fringe, as if they alone corresponded to the fixed cheeks of the Opisthoparia and Proparia, or even included also the free cheeks of these orders. But if the facial suture is marginal, and if the lower plate of the fringe is considered to represent the free-cheeks, as Beecher’ maintained, the upper plate of the fringe must be regarded as merely a modified marginal portion of the fixed cheeks, so that the triangular areas within the fringe would only constitute the inner part of the fixed cheeks. Whether we regard this view of the homologies of these structures as correct or not (see below), we must note that there is sometimes no sharp demarcation of the fringe from the so-called cheeks, scattered pits (particularly near the genal angles) occurring within the generally regular inner limits of the fringe, as for instance in T. concentricus of the Onny River (Guot. Mae., Dec. V, Vol. IX, p. 349, Pl. XVIII, Fig. 4, 1912). It is, however, convenient to describe these so-called cheeks apart from the fringe, the characters of which have been discussed on a previous occasion (op. cit.), and we may accordingly term them the genal areas to avoid confusion and premature conclusions. There are three more or less distinct types of genal areas recognizable amongst the species of Zrinucleus, 1.e. : 1. Genal areas divided into two more or less unequal portions by an oblique ridge or line of bending, each portion having a different surface ornamentation, ro a Murchisont, T. Gibbsi, T. Htheridger. 2. Genal areas marked with a horizontal or slightly oblique line (‘‘ocular ridge” or ‘‘line’’) running outwards from: the side of the glabella to a median or submedian tubercle (‘‘eye’”’ or ‘‘ocular tubercle’’) and sometimes beyond it. The ornamentation of the surface is uniform. E.g. 7. setv- cornis, T. Bucklandt. 3. Genal areas without any ridge or line, uniformly convex, without ‘‘ocular tubercle”. ‘The ornamentation of the surface is uniform. E.g. 7. concentricus. These three types may now be described in detail, and their development and relations studied in various species. 1. In Z. Murchisoni, Salter (see Grou. Mac., Dec. VI, Vol. I, p. 352, Pl. XXVIII, Figs. 4, 4a, 1914), a narrow semilunar area stretches along the inside of the fringe from the pseudo-antennary pits at the front end of the glabella to “the postero-lateral outer angle of the genal area, and is marked off from the rest of the genal area 1 Beecher, Amer. Journ. Sci., ser. IV, vol. iii, pp. 100, 103, 183, 186, 1897. F. R. 0. Reed—On the genus Trinucleus. 119 by a nearly straight oblique line along which the surface is bent or angulated. The semilunar outer band thus formed slopes down more or less steeply to the fringe, and is differentiated from the rest of the genal area. The line of angulation is marked at its posterior end by a short ridge forming its crest, beyond which lies a deep pit in the pleuro-occipital furrow. Salter’ considered that this line of angu- lation occupied the place of the facial suture of other trilobites. The semilunar outer band is smooth in the species 7. Murchisont, but the whole of the inner portion (with the exception of a narrow region alongside the basal part of the glabella) is covered with a coarse reticulation of fine raised lines which arise as a fan-like group of thicker lines radiating from a small notch behind a tubercle projecting into the axial furrow at the level of the first lateral furrow of the glabella. These radiating lines rapidly break up into the general reticulation of the surface, so that the radial arrangement is almost lost. The pseudo-frontal lobe of the glabella, which possesses a median tubercle, has similar fine reticulation, but anteriorly the meshes are elongated transversely so as to be roughly concentric to the front end; posteriorly they became hexagonal or polygonal lke those on the genal areas. The small inner portion of the genal area on each side of the base of the glabella is only minutely granulated, which is significant (see below). In Z. Gibbst, Salter, and 7. Etheridge, Hicks, the angulation of the genal areas and differentiation into two portions exhibit the same general characters. But in the former species the angulation is sharper and the outer band narrower, and the fan-like arrangement of the reticulating lines on the posterior part is not so clear. In 7. Htheridgei the genal areas are divided into two nearly equal parts by the angulation, but itis less sharply marked and often nearly obsolete. The different superficial characters of the two parts are, nevertheless, retained. No definite point of origin for the reticulations ‘ean be recognized in this species, a general honeycomb-like meshwork existing all over the inner region with the exception of the inner posterior angle alongside the base of the glabella, which is smooth. A median tubercle is usually visible on the pseudo-frontal lobe of the glabella. In none of these three species is there a definite ocular ridge or ocular tubercle on the genal areas. It appears probable that we may correctly compare the radiating and reticulating lines on the surface of the genal areas with the so-called nervures or veins on the cheeks of Dionide (although their radiating arrangement is better preserved in the latter genus), for they arise from the same point on the axial furrows. Similar structures having an identical origin are found in the cheeks of many Cambrian genera, which are devoid of compound eyes, e.g. Hrinnys, LElyx, Liocephalus, and other members of the Conocoryphide. Beecher regarded the meshwork and lines as belonging to the nervous system, but Lindstrém? considered them as ramifications of the circulatory system, the larger lines being the main vessels and 1 Salter, Mem. Geol. Surv., vol. iii, 2nd ed., p. 516, 1881. 2 Lindstrém, Kongl. Svensk. Vet. Akad. Handl., Bd. xxxiv, No. 8, pp. 18-20, 31-3. 120 F. R. C, Reed—On the genus Trinucleus. the smaller ones representing capillaries and venules as suggested by the genus Limulus. It can hardly be doubted that the general reticulation of the surface is not merely a superficial ornamentation of the shell of no functional importance, particularly when we are able to trace its direct connexion with a definite group of radiating vessels always arising from the same spot on the axial furrows. The small smooth or ciierenly, ornamented regions close to the base of the glabella suggest the ‘alar areas’ of Harpes and Dionide, which are also traceable in some species of Ampyax and are found clearly developed in larval stages of TZrinucleus as Beecher’ demonstrated. The nature and history of the semilunar outer band in front of the angulated line crossing the genal areas is intimately bound up with the whole interpretation of the structure of the head-shield of the genus. But before discussing this vexed question it will be best to describe the characters of the two other groups into which I have divided the species according to their genal features. It may, however, be naturally expected that in the earliest representatives of the genus which are comprised in my first group, and are confined to the Arenig and Llandeilo Beds, we should find the evidence of its affinities and original structure. Later species in the stratigraphical succession would be expected to diverge more — from the primitive stock and to have suffered additional modification. There is a link connecting the first group with the second, and it is found in the species Z. fimbriatus, Murchison, the position of which is intermediate. For it has no division of the genal areas into two parts by a line of angulation, their surface being gently and uniformly convex; there is no ocular tubercle and no typical ocular ridge, though Salter? and McCoy.* put this species in the genus Zretaspis, which is characterized by their possession. The diagonal facial suture which McCoy‘ clearly represented in his figure does not exist. There is, however, a small tubercle in young individuals® situated in - the axial furrow opposite the first lateral furrow of the glabella, just as in 7. Murchisont, but there is no such definite group of nervures radiating from it. over the genal area. We may, however, observe that near the posterior lateral angles of the genal areas the inter- lacing sinuous lines, which form the reticulations on the surface, converge and are grouped together to form larger, more elongated meshes directed towards a small tubercle near the posterior border with a pit in the pleuro-occipital furrow, asin 7. Murchisoni. The inner posterior angles are also nearly smooth with pees faint or obsolete reticulations, thus affording traces of the ‘alar areas’ The rest of the genal areas is covered with a polygonal or hexa- gonal fine meshwork. ; The French species 7. Bureaut, Oehlert,* which seems to belong 1 Beecher, Amer. Journ. Sci., ser. 111, vol. xlix, pl. iii, figs. 1, 2, 1895. ®? Salter, Dec. Geol. Surv., vii, pl. vii, fig. 8, 1853. * McCoy, Syn. Brit. Pal. Foss. Woodw. Mus., p. 146. * Ibid., pl. in, figs. 16, 16a. ° Reed, GEOL. MAG., Dec. VI, Vol. I, Pl. XXVIII, Fig. 3, 1914. ® Oehlert, Bull. Soc. géol. France, ser. WI, vol. xxiii, p. 308, pl. i, fig. 7, 1895. F. R. C. Reed—On the genus Trinucleus. 121 here, is of interest from possessing two well-developed raised nervures on the genal areas, starting from a point on the axial furrow alongside the pseudo-frontal lobe, and then diverging as they cross the genal areas to converge and unite a little in front of the posterior lateral angle. These structures are undoubtedly of the same nature as those described in 7. Murchisont and 7. fimbriatus, having the same point of origin, same general course, and same point of termination; and they bear a specially close resemblance to the nervures on the cheeks of Dionide Lapworth, Etheridge, jun., and Nicholson,’ from the Whitehouse Group of the Girvan district. The rest of the genal surface of 7. Bureau is said to be smooth or minutely punctate, and no reticulating lines are described. Ocular tubercles are absent. 2. We pass now to consider the typical members of the second group in which a definite ocular ridge and ocular tubercle is developed in each genal area. These structures find their expression in most of the members of McCoy’s genus Zretaspis. The ocular ridge starts at the level of and opposite the first lateral furrow of the glabella, and thus corresponds in place of origin with the marginal tubercle and commencement of the radiating lines in Z. Murchisoni and its. allies. Usually the ridge ends in a small tubercle called the ocellus or ocular tubercle by most authors, and it may run out at right angles to the axial furrows or be directed rather obliquely backwards towards the postero-lateral angle. It is occasionally continued beyond the ocular tubercle to this point with diminished strength, as may be seen in the smaller specimens from Thraive Glen, Girvan, which are attributed to 7. Bucklandi, Barr. In these this extension of the ridge ends against the fringe a little in front of the postero- lateral angle of the genal area. Nicholson & Etheridge, jun.,” noticed and described this feature in this Scotch species, and the present author * has also described it in 7. subradiatus from the same area. Ruedemann‘ has observed its occurrence also in JZ. reticulatus, Ruedemann. The inner and outer portions of the ocular ridge do not correspond in position or course with the line of bending which crosses the genal areas in the first group; but as above pointed out the point of origin of the ocular ridge coincides with that of the group of nervures. © Not only may the outer portion or extension of the ocular ridge disappear, as is the case in the large form of 7. Bucklandi from Girvan, but the inner portion between the axial furrow and ocular tubercle may likewise become obsolete, leaving the latter isolated. Since the young of 7. concentricus (Eaton) possesses an ocular ridge (but not its extension) as well as an ocular tubercle, according to Beecher,*® both structures have been held to be phylogenetically primitive characters; and if this is sothe loss of the outer and inner 1 Reed, Girvan Trilobites (Paleont. Soc.); pt. i, p. 25, pl. iv, fig. i, 1903. * Nicholson & Etheridge, Mon. Silur. Foss. Girvan, fase. 2, p. 191, 1880. 3 Reed, Girvan Trilobites, pt. i, p. 12, pl. ii, figs. 1-6, 1903. 4 Ruedemann, Bull. 49 New York State Museum (1901), Paleont. Papers 2, p. 41, pl. iii, figs. 11, 15-20. ° Beecher, Amer. Journ. Sci., vol. xlix, p. 309, pl. iii, 1895. 122 F. R. C. Reed—On the genus Trinucleus. portions of the ocular ridge mark a more advanced stage in develop- ment. To this question we will return later. With regard to the function of this structure Beecher (op. cit.) remarked that “from the direction of the optic nerve in Zimulus and its relations to the surface features of the cephalothorax, the eye-line [ = ocular ridge! probably represents the course of that nerve”. The Bohemian examples of 7. Bucklandt, according to Barrande, do not possess an ocular ridge, the ocellus being isolated on the genal area. It may be suggested that the ocular ridge in this Group 2 with its outward extension represents a specialized and concentrated nerve- supply and corresponds to a specially enlarged nervure of the diffuse radiating bundle of nervures in Group 1. Its presence is probably correlated with that of the ocelli; and the absence of visual organs in Group 1 seems to be connected with the breaking up and irregular extension of the nerves over the whole surface, since we find a similar condition in many blind Conocoryphide. Inthe large Girvan examples of Z. Bucklandi in which the ocular ridge is obsolete the reticulating lines which cover the genal areas with a polygonal meshwork start as radiating or sinuous nervures from the same point on the axial furrows as the ocular ridge and as the corresponding nervures in Group 1. ‘The extension of the ocular ridge to the postero-lateral angles which, as above-mentioned, occurs in several species may likewise be the concentration of the nerve-supply which in Group 1 and 7. fimbriatus is split up into a convergent group of fine lines. The phylogenetic significance of these structures is discussed below. A few remarks may here be made on the puzzling variations in the development of the meshwork on the genal areas which is found in this second group. The surface in some cases is covered with the reticulating ornament, but in other cases appears smooth or punctate ; and internal casts likewise differ much in their appearance. These peculiarities amongst individuals of the same species or members of the same group are due to the existence of more than one layer in the shell and to the difference in the characters of the outer and inner surfaces of these layers. It seems that there are two layers to the shell, the outer one of which has an externally smooth or punctate surface, and is usually very thin and easily abraded, so that it is frequently missing from even well-preserved specimens. ‘The second or inner layer bears on its upper surface (which is in contact with the lower surface of the outer layer) the raised lines of the reticulating nervures, while the lower surface of the inner layer is only minutely granulated or smooth, the interlaminar nervures rarely showing through it. When, how- ever, this inner layer is thin and the nervures stout and strong, we find the reticulations showing through, and therefore impressed on the internal cast of the head-shiel ld, the ‘hexagonal or polygonal cells being represented as shallow pits, as can be seen in casts of Te Bucklandi from Girvan or of 7. seticornis from various English and Welsh localities. The nervures do not seem usually to project as raised lines on the inner surface of the inner layer; and the ocular ridge and tubercle are certainly hollow, for these structures show respectively as a groove and a pit on internal casts. When Notices of Memoirs—Heterangiums vm Coal-measures. 128 the inner layer is thick and granulated, the internal cast is covered with corresponding small puncte. Barrande’ was much puzzled with these different appearances of the cheeks and ‘glabella, and did not offer any satisfactory explanation of them. 3. In the third group intv which I have arranged the species according to their genal characters, the adults have no ocular ridges and no ocular tubercles, and the reticulating nervures seem also to have disappeared, the shell being smooth and the interlaminar surfaces showing no meshwork, though puncte or minute granulations may be present. But in some of the largest specimens of 7. concentricus from the Oany River there are faint relics of the meshwork. The internal casts as well as the external surface of the shell only show minute pits or granules as a rule. In the young of TZ. concentricus the ocular ridge and ocellus of the species of Group 2 are present, according to Beecher, so that their loss seems to be a secondary modification or a suppression of larval characters; for the strati- graphically later group of 7. se¢icornis possesses them. (To be concluded in our next Nwmber.) NOTICHS OF MEMOTRS. {.—Tse Hererancioms or tae British CoaL-mEasurES. By Dr. D. H. Scorr, For.Sec.R.S. JILLIAMSON, in his published papers, only recognized two British species of Heterangium, Grievii and H. tiliwoides. Under the former name he included not only the Lower Carboniferous plant from Burntisland, on which the species was founded, but also certain Coal-measure forms from Dulesgate. In the joint work by Willamson and the present author the same nomenclature was adopted, but a second form from Dulesgate was also described under the provisional name H. cylindricum. HT, tiliwoides, a Coal-measure species from Halifax, remarkable for the great development and perfect preservation of the phloem, has been kept distinct ever since its first discovery in 1886. The enormous difference of age between the Burntisland and the Dulesgate plants rendered their specific identity highly improbable, and the latter has been separated under the name H. Lomazxii, originally suggested by Williamson himself, after the name of the discoverer, though not published. H. Lomaxii is characterized by the great distinctness of the primary xylem-strands, by their nearly exarch structure, with little primary centrifugal wood, by the abundant secretory sacs of the stele, and by the rather scattered leaves. In the Dulesgate material several forms of Heterangium stem have been found in association; it is unlikely that they are specifically distinct—they more probably represent axes of different orders. The provisional species H. cylindricum differs in no important respect from LH, Lomaxit, to which it should be reduced. 1 Barrande, Syst. Silur. Bohéme, vol. i, Trilob., p. 622; ibid., Suppl., p. 47. 124 Notices of Memoirs—The Geology of Porewpine. A very fine Heterangium from Shore was discovered by Mr. Lomax and his son in 1912. It is of large size, at least 17 mm. in diameter, though without secondary growth. The plant was originally compared with the so-called H. cylindricum, but is at least as close to H. tulieoides. The feature which at first seemed to be most striking is the fact that four distinct leaf-trace bundles enter the base of the leaf, each of them dividing into two in the petiole. This is certainly the best example yet found of a polydesmic petiole in Heterangium, and shows an interesting approach to the Medullosez in this respect. We may also compare Dr. Gordon’s new genus Rhetinangium. However, there is reason to believe that most of the British Coal- measure Heterangiums were polydesmic. In JZ. tilieoides there are four distinct bundles in the petiole, and the same was the case in H, Lomaxii. In all these plants two bundles start from the stele to form the leaf-trace, dividing into four, at least in some cases, before entering the leaf-base. Only in a very small stem from Dulesgate (not associated with H. Lomaxit) did a single bundle leave the stele (as in the Burntisland species), dividing into two on its outward course. This. little stem has nothing to connect it with any other form and may be distinguished as H. minimum. H1. tilieoides is maintained as a distinct species, mainly on the ground of its highly developed phloem with dilated medullary rays. In the behaviour of the leaf-traces it comes very near the Shore plant, which may, for the present at least, be kept distinct under the name HI. shorense. II.—Nore on tHe Guronogy or Porcuprne.! By J. B. Tyreext. HAVE been asked on two or three occasions whether I consider that the gold-bearing quartz veins in Porcupine are formed by the filling of fissures or by replacement of the rock in which they occur, and I have told individual members of an instance where bodies of quartz were undoubtedly introduced into similar pre- Cambrian rocks by metasomatic replacement, but some others among those present might be interested in hearing of the instance, so I will mention it. In the West Shining Tree country greenstones showing strongly marked ovoidal or pillow structure, similar to that so common in the amygdaloidal basalts of this district, are particularly abundant, and here and there through the greenstone quartz veins. occur, some of which have been determined to contain gold. The. individual ovoids or pillows are packed closely together, but there are angular portions of the greenstone in between them, and, as a rule, the rock inside the pillows and in the angular areas outside of them are almost precisely similar in character. In one place, however, the angular areas are entirely converted into quartz, which, as far as I could see, was precisely similar to the quartz in the veins. near by. As these angular areas had originally been greenstone, we have in them a clearly marked example of a metasomatic replacement. 1 Extract from the Monthly Bulletin of the Canadian Mining Institute, June, 1915, pp. 397-8. Reviews—J. B. Scrivenor—Geology of Malay States. 125 of the greenstone by quartz, but whether the veins in the vicinity were also formed by a similar replacement or not, I have no definite proof, but I believe that replacement took a large share in their formation. A number of the members here may think that such questions have no bearing on mining problems, and I have often heard men say that they did not care how the gold got into the rocks, that all they were interested in was where it was. Now the world has advanced too far to ignore the causes of things; if those things are to be clearly understood and if you are to clearly understand the bodies of ore which you are working you cannot afford to ignore the question of the causes which lead to the formation of those ore bodies, since a knowledge of those causes may enable you to correctly predict the extensions “of those ore bodies or may point y you to where other similar ore bodies occur. RAV LH ws. 1.—Geotocy oF THE FeperareD Matay Srates. Geologists’ Annual Report for the year 1914. By J. B. ScrivEenor, Geologist F.M.S. ARLIER reports, e.g. that for the period September, 1908, to January, 1907 (reviewed in the Groroeican Magazine, 1907, pp. 565-7), have given British geologists an opportunity of becoming acquainted with the general geology of the Federated Malay States, while Mr. Scrivenor’s finely illustrated report, Zhe Geology and Mining Industry of the Kinta District, Perak (1918), has described the district which is most interesting and important both geologically and economically. The present report, which deals principally with economic questions, is a record of steady progress, though it does not include any startling discoveries. There is only a brief reference to the field work of Mr. Scrivenor in mapping the Batang Padang district. Such work is bound to be carried out under many difficulties in view of the climate and of the dense vegetation which covers so Hee of this country. Scrivenor took the opportunity a accompanying the district os of Upper Perak in a journey to the little-known region near the headwaters of the Perak River. He briefly describes the country as an area of granite at no great elevation, supporting masses of altered bedded rock with quartz porphyry and basic volcanic rocks. The report shows that the chemist, Mr. C. Salter, has been occupied with economic work, chiefly assays for minerals, but including also a number of analyses. It is satisfactory to learn that Mr. Scrivenor is getting together a collection of photographs illustrating the geology of the country. The author describes a successful attempt to replace the diamond by local corundum for drilling purposes. A consignment of kaolin was shipped to Kurope in order to ascertain if it could be used for pottery. Unfortunately, owing to the War, half the consignment failed to reach its destination. Not much further information is given concerning the greatest industry of the peninsula, that of tin-mining, and no further light is 126 Reviews—H. Jeffreys—Interior of the Earth. thrown on the question of the age and origin of the tin-bearing clays of the Kinta district, concerning which Mr. Scrivenor’s former assistant, Mr. W. R. Jones, is in disagreement with him. There is a brief account of gold workings under native management. The statement that certain men ‘‘obtained in a season 2-3 katis of gold per party of three men. This is equal to 24-36 bungkals of gold”’ does not convey much information to the average reader of the report at home. Such words as prkul and ulu might also with advantage be explained in a footnote. IJ.—Txe Inrerior or THE Harta. Certain Hyporueses as To THE InTERNAL SrRucTURE oF THE Kant anD Moon. By Harrorp Jerrreys, B.A., M.Sc. Mem. Roy. Ast. Soc., lx, pt. v, pp. 187-217, 1915. Tue Viscosrry or THE Earta. By H. Jerrreys. Monthly Notices Roy. Ast. Soc., xxv, pp. 648-58; Ixxvi, pp. 84-6, 1915. Tue MecwanrcaL Propertizs or THE Karta. By H. Jerrreys. The Observatory, No. 491, pp. 347-51, 1915. laa gradual refinement of geophysical methods of research during recent years has resulted in the accumulation of quite a considerable fund of information relating to the interior of the earth. The known data from which our present knowledge is derived are—(1) the value of the precessional constant, (2) the earth’s superficial ellipticity, (8) the period of the variation of latitude, (4) the observed heights of oceanic tides, (5) the lunar deflection of gravity, and (6) the velocities of earthquake waves. Using the results available from these sources, Mr. Jeffreys discusses those hypotheses that regard the earth as consisting primarily of a metallic core surrounded by a rocky sheli, particularly from the point of view of determining the distribution of rigidity and density. He shows that neither the outer shell nor the inner core can be permanently rigid, and that the only conclusion consistent with the facts is that the earth as a whole is plastic. Again, the only distribution of density conformable with this conclusion is that of Wiechert, viz. a shell of density 3:2 surrounding a core of density 8-2 having a radius equal to 0°78 that of the surface. These figures are, of course, closely in accordance with the densities of stony and iron meteorites, and with the facts deduced from the seismic exploration of the earth’s interior. That the rigidity of the core is at least twice that of steel is a necessary consequence of the effect of pressure, if the main constituent of the core is metallic iron. Mr. Jeffreys shows that the lithosphere has the hydrostatic form to a high degree of accuracy. This fact, combined with the deduction that the earth’s rotation was originally faster than now, leads us to conclude that the outer shell (at least) must have periodically adjusted itself to the hydrostatic form. Chamberlin has rejected this view, partly because it seems to imply that mountain ranges—particularly the older ones—should be meridional in their alignment. However, it seems to the present writer that the greatest adjustment may — have occurred in a period antecedent to any now recognized. Such Reviews—Fossil Manumals from China. 127 adjustment, if accomplished mainly by movements of igneous magmas, would well explain the north to south elongation of the continents. Moreover, in this way one can understand the predominance of granitic rocks in the lighter continental segments, as compared with the suggested paucity or even absence of granitic rocks from the heavier oceanic segments, In his consideration of the moon, Mr. Jeffreys finds that the period of revolution at the time of its consolidation was of the order 6°5 days. An important conclusion to which he arrives is that the strains within the moon can never have been sufficient to produce permanent set. It thus becomes difficult to believe that tidal friction has been responsible for the moon’s present attitude towards the earth. In the second paper it is shown that the moon’s empirical secular acceleration leads to such a value for the plasticity of the earth that the Eulerian nutation (responsible for variation of latitude) ought to. die down ina few days. One explanation of the obvious discrepancy would be that tidal friction is not the main factor now concerned in the control of the moon’s secular acceleration. It is interesting to notice that none of these investigations prove a formerly molten earth, though it is safe to say that with such an assumption the present status and behaviour of the earth and moon ean be most easily explained. : Artuur Hormes. TIT.—(1) Ow some Fosstr Mammats From Szn-cuuan, Cutna. (2) On some Fosstu Mammats From Honan, Curna. (3) Ow some Fossin Mammats From 'l'suxinoxt, Uco. By H. Marsvomoro. Reports of the Tohoku Imperial University [2], Geology, vol. ii, No. 1, 1915. ‘{\HE first of these papers deals with mammalian remains from the late Pliocene and early Pleistocene deposits. From the former _two species of Stegodon are recognized, together with a Rhinoceros and several Bovine animals, one of which is referred to a new genus Proboselaphus. From the latter horizon a new form of Hyena, H. ultima, and two species of Rhinoceros are described. The second paper describes a number of Pleistocene mammals, including a large species of Hqwus, regarded as new, two species of deer, and a small Bison, referred to a new species under the name Bison exiguus. There is also a human sacrum which is said to resemble in several respects the sacrum of the Chapelle-aux-Saintes man described by Boule. The last paper gives an account of a series of mammals from the Pleistocene of Japan, including Elephas namadicus and a new species of pig, Sus nipponicus, in some respects intermediate between Sus tatwanus and S. leucomystax. - The above papers, which are published in English, are beautifully illustrated by a series of nineteen plates, for the most part unusually good photographs, and some text-figures. 128 Reviews—Mammoths and Mastodons. IV.—Mammorus anp Masropons. By W. D. Marruew. No. 43 Guide Leaflet, American Museum of Natural History, November, 1915. [* this guide leaflet Dr. Matthew has given a very interesting outline of our present knowledge of the Proboscidea, referring especially to the specimens exhibited in the American Museum of Natural History. He commences with a short historical account of the early discoveries of elephant remains, and then passes on to a brief description of the various extinct elephants, the American Mastodon, and the Tertiary Mastodons, concluding with a discussion on the early ancestors of the group and the general course of its evolution. One of the most interesting sections is that relating to the American Tertiary Mastodons, concerning which much more information than has yet been published is desirable. The author revives several forgotten generic names, e.g. Gomphotherium and Rhynchotherium, im the last case mentioning no species. Probably, however, the species described in this Magazine ([5] Vol. VI, p. 347, 1909) under the name Tetrabelodon dinothertoides should be placed here, the symphysial part of the mandible being deflected in the manner said to be characteristic of the genus. Jeritherium is not regarded as a direct ancestor of the Proboscidea, but, although it may be a side branch, its Proboscidean affinities appear to be incontestable. The pamphlet is illustrated with a plate and eleven text-figures. V.—New Evryrrerrp Horton.—A Eurypterid in the Barton Beds! Sounds startling. And a coral-reef too!—Gently, gentle reader, these Barton Beds are in North America. Oh! But then, you will say (after some research) they are Stevenson’s Barton group in the Carboniferous of Pennsylvania. No, they are in Ontario, south of that superbly patriotic city Hamilton, and they lie at the very top of the Niagara formation. Fortunately Mr. M. Y. Williams (Oct., 1915, Canada Geol. Surv. Mus. Bulletin, No. 20) now proposes for them the name Eramosa beds, because their dark bituminous dolomites and shales are well exposed along the Eramosa River between Rockwood and Guelph. The importance of these beds lies in their paleontological evidence of a conformable passage from the Niagara to the Guelph formations. The Eurypterid, Husarcus logant, n.sp., is based upon various fragments, and since these are associated with fossils of marine origin, Mr. ‘Williams believes that the, arthropods ‘‘lived in an entirely - marine habitat ’’, a conclusion that would have been less open to criticism had the fragments been less fragmentary. In the descriptions of species contained in these excellent Bulletins, would it not be possible to give some indication of their systematic position? How many geologists, or even professed paleontologists, ean say off-hand what ZLichenalia concentrica is? Mr. Williams tells them that the surface is undulatory and bears radial and concentric strie about 0°5 mm. apart; but he leaves them to their own devices to find out that it is a Wace pare 3S Bryozoan, closely allied to Listulipora. it i me el it tarts ee a ee, Reviews—Effects of Drought in the Waterberg. 129 ViI.—Errects oF Drovucut IN THE WaTERBERG, TraNsvAaL.—The Smithsonian Report for 1914 has reprinted from the Agricultural Journal of South Africa a paper by E. N. Marais on the effects of drought in the Waterberg, which has converted over 4,000 square miles of the Northern Transvaal, an area equal in extent to the ‘Orange Free State, once rich in orange groves, and formerly ‘a sort of lotus land of fertility, literally overflowing with milk and honey ”’ into an absolute desert ‘‘in which there is no single drop of water running or stagnant above the surface of the ground’’. He says the Limpopo River is now dry throughout this district, and water can only be obtained from it by deep sinking in its bed. All the ordinary ‘springs are empty, and it is only the thermal springs which are still flowing; they show no change in volume, though the loss of their water between the spring and the dam is 60 per cent greater than formerly. The animals have changed their habits or been extermi- mated; the vegetation is dead, and most of it has disappeared. The author refers to the hope that this extreme drought may mark the greatest swing of the pendulum towards desiccation and may be followed by improvement; but he remarks that every fact observed indicates that the change is permanent, and ‘‘ that the oscillations of the pendulum are gradually lessening round the dead point”. He regards this desiccation of the Northern Transvaal as part of a climatic change, which in the last fifty years has turned thousands of square miles of once fertile territory in Asia into desert. Mr. Marais’ descriptions are more graphic than convincing. His statement as to the habits of baboons’ are either exaggerated or refer to a local peculiarity ; and it is difficult to take many of the author’s statements seriously, as when he warns us that on the drying up of Lake Rudolf, “that most perfect diadem in the girdle of the globe . largely depends the fate of the Nile and of fertile Egypt.” Lake Rudolf contributes no more water to the Nile than it does to the Mississippi, and as the author’s African geography is so imperfect his conclusions on Asiatic climate do not carry weight. VII.—Crimate oF Grotogic Trme.—Professor Schuchert’s ‘‘ Climate ot Geologic Time”’ has been reprinted from Huntington’s Climatic Factor (1914, pp. 265-89) in revised form in the Smithsonian report for 1914, pp. 277-311. The paper is a valuable summary of the chief factors as to the past variations in climate. There are no references, but as the authors’ names are quoted the authorities can be easily traced. The literature on the subject is so scattered that some is omitted, and the knowledge displayed from different parts of the world is unequal, but probably no geologist, even though specially interested in this question, can read the paper without finding much fresh. information. The author insists that the South Australian Boulder-clays are pre-Cambrian instead of Cambrian, and accordingly holds that there is no evidence of refrigeration of climate i in Cambrian times. He accepts the view that ‘‘ the typical glaciation ”, including perfect roches moutonnées and thousands of perched blocks in Western Ross and Sutherland are due to a pre-Cambrian and not to the DECADE VI.—VOL. Il.—NO. III. 9 130 Reviews—The Glacial Anticyclone. Pleistocene glaciation. He adopts from paleontological evidence great climatic variations in the Mesozoic, but regards Neumayr’s Jurassic climatic belts as rather faunal realms. A universal warm | climate in the Middle Jurassic he claims from the far northern distribution of coral reefs and marine saurians, though why the saurians could not have lived in cold water, and the locality of the far northern Middle Jurassic coral reefs, is not stated. The identity of the tree ferns in Western Antarctica and Yorkshire does not appear to necessitate a universal warm climate, especially considering Hooker’s emphatic warning against trusting to ferns as climatic guides. The paper is of chief value as a summary of the opinion of one of the most competent authorities on paleontological evidence as to former geographical conditions. He concludes that there have been at least seven cool and four Glacial periods in the earth’s history, and that these were short in comparison with the intervening warm periods. In discussing the causes of the climatic changes he rejects volcanic dust as a primary factor, and also variations in the amount of carbon dioxide in the atmosphere. He regards the most probable cause as geographic changes due to rhythmic alteration in the earth’s topography, and he regards favourably the conclusion that there has been a periodic alternate heaping up of the ocean waters in the equatorial and Polar regions. He asks in conclusion, ‘‘ are we not forced to conclude’ that the earth’s shape changes periodically in response to gravitative forces that alter the body forms?” VIII.—Tue Guactat Anricyctonr.—The growing belief that the former glaciations are to be explained by changes in the atmospheric circulation and especially by the influence of great stationary anti- cyclones is supported in an interesting paper by Professor W. H. Hobbs, ‘‘ The Role of the Glacial Anticyclone in the Air Circulation ot the Globe” (Proc. Amer. Phil. Soc., vol. liv, No. 218, pp. 185-225, 1915). Professor Hobbs is already well known as one of the upholders of this view, and he here discusses the bearing of the recent results from Antarctica and those collected by expeditions across Greenland which have not received adequate attention. Antarctica appeared at first opposed to this explanation owing to the belief that a great permanent cyclone lay around the South Pole. So strongly was this view accepted that Meinardus of the German Antarctic Expedition predicted that the interior of the Antarctic continent was bare and snowless. Meteorologists cling tenaciously to the South Polar cyclone. The results of the National Antarctic Expedition on this question were ambiguous owing to doubt as to whether the critical wind directions recorded were from the true or the magnetic south, directions which there are almost directly opposite. The work of the later expeditions has replaced the supposed South Polar cyclone by an anticline and has shown the existence of a powerful fohn effect around Antarctica, as is there also around Greenland. Professor Hobbs discusses the observations of the Swiss expedition under de Quervain, who in 1912 crossed Greenland from west to east between latitude 66° and 68° N.; and of the German expedition under Koch and Reviews—Shketch of the Life of Eduard Suess. 131 Wegener, which in 1912-138 crossed between latitudes 72° and 78°. Professor Hobbs’ valuable memoir indicates that glacial geology will _ be advanced most from recent Polar work by the meteorological evidence. TX.—Sxerca or tHE Lire or Epuarp Svuzss (1831-1914). By P. Trrurer. Smithsonian Report, 1914, Publication 2358, pp- 709-18. (¥\HE Smithsonian Report for 1914(pp. 709-18) includes a translation of the admirable sketch of Suess by Professor Termier, the Continental geologist who most approaches Suess in what has been called his geopoetic style. Professor Termier’s sympathetic and luminous eulogy lays stress on Suess’ Jewish origin, on the difficulties he encountered as a student in Vienna, which nearly drove him into commercial life, on his useful service in the municipal and national polities of Austria, on his two works, Die Hnstehung der Alpen and Das Anthtz der Erde, and on the intuitive nature of his mental methods. Professor Termier insists that the volumes of the Antilitz ‘‘contain scarcely any theories”. The author, he says, ‘‘does not seek to explain or convince—he shows.” He defends Suess from the criticism that on many controversial questions he adopted an indecisive and timid attitude, on the ground that Suess was never a theorist, that he did not care to argue on scientific matters, for he was content with seeing, and, having seen, with showing. He claims that Suess ‘‘ did not say all, he made few personal observations, he did not foresee everything, but by his intuitions, truly those of a genius, of relations and their causes, he incited, prepared, made possible decisive observations, observations which have revolutionized our ideas and illuminated our knowledge”’. JE Wee Ge X.—BrisiiograPuy oF YorksHire Grotogy. Forming Proceedings of the Yorkshire Geological Society, vol. xiii. C. Fox-Strangways’ Memorial Volume. By ‘Il. Suevparp. 8vo; pp. xxvi, 6380. London, Hull, and York, 1915. Price 15s. net. T the time of his death Mr. Fox-Strangways had accumulated an y incomplete MS. towards a Bibliography of Yorkshire Geology from 1534 to 1892. This has been revised and brought up to 1914 by Mr. Sheppard of Hull, who has for many years contributed annual lists to the Waturalist. That it should be printed and issued by the Yorkshire Geological Society is an evidence at once of its value and the wisdom of that Society. Yorkshire geologists have now an encyclopedic work to hand to further their efforts and to save their time. Works are arranged chronologically, then follows a list of the maps and sections of the Geological Survey, and finally an index of 1380 double-column pages which gives subjects and localities much in the same way as the Annual Lists of Literature received by the Geological Society of London. It will be of extreme value to all local workers and scarcely of less to those at a distance, 132 Reports & Proceedings—Geological Society of London. and is a really noble monument to Mr. Fox-Strangways, who did so much for Yorkshire geology. Mr. Sheppard has performed his share well, and thanks are especially due to him for undertaking so heavy an addition to his many burdens. We only wish so excellent an example will have imitators in many other of our county societies, for bibliography is a very sure and certain method of helping others and preventing duplication of work. XI.—Sitvrran or tHE Lower SasxarcHewan.—From the Grand Rapids, from Cedar Lake, and from cuttings along the recently constructed Hudson Bay railway, various Silurian horizons are reported on by Dr. E. M. Kindle (Oct., 1915, Canada Geol. Surv. Mus. Bulletin, No. 21). Among Brachiopods two new species of Leptena (LZ. sinuosa and L. parvula) are described from beds of late Silurian age, equivalent to the Stonewall Limestone. A dolomite near the base of the Silurian at Grand Rapids abounds in Conchidium decus- satum. The numerous ventral valves of this Pentamerid show variation in three well-marked directions, but intermediate forms are so numerous that no distinct varieties can be recognized. In a word the variation appears continuous. The spondylium reaches approxi- mate maturity at an early stage, but the radiating folds continue to increase in strength and number down to extreme old age. REPORTS AND PROCHHDIN GS. I.—GeronogicaL Socrery or Lonpon. 1. December 15, 1915.—Dr. A. Smith Woodward, F.R.S., President, in the Chair. Dr. Aubrey Strahan, F.R.S., gave an account of a deep boring which was made in 1918 in search of coal, in the parish of Little Missenden, at an elevation of 459 feet above sea-level. The collection of specimens and the identification of fossils was carried out by Mr. J. Pringle. For the first 1,200 feet the hole was punched, and nothing is known of the strata traversed down to that depth—beyond the fact that the boring started in the top of the Middle Chalk and passed through some Oxford Clay and, below that, some oolitic limestones which presumably belong to the Great Oolite Series. From 1,200 feet the hole was drilled for 64 feet, and cores were preserved. The cores consisted of alternations of limestone and mud- stone, with a rich and characteristic Upper Ludlow fauna. Among the fossils was Orthoceras damesi, Roemer [? Krause], which had not previously been obtained in this country. The boring serves to fix part of the northern boundary of the tract of Old Red Sandstone which underlies London. It is intended to publish a full account in the next issue of the Summary of Progress of the Geological Survey. Reports & Proceedings—Geological Socrety of London. 133 2. January 5, 1916.—Dr. A. Smith Woodward, F.R.S., President, in the Chair. The Secretary read the following communication :— ‘The Islay Anticline (Inner Hebrides).”” By Edward Battersby Bailey, B.A., F.G.S., 2nd Lieut. R.G.A. The observations made by Peach, Wilkinson, Thomson, Macculloch, and others in regard to the ‘ Schistose Islands’ of Scotland are passed in review, and many of them confirmed. In certain directions, however, new interpretations are offered. The following suggestions are among those put forward :— 1. An important fault, perhaps the Great Glen Fault, passes through the hollow separating Colonsay and the western peninsula of Islay from the rest of the archipelago. 2. The dolomitic ‘Fucoid Beds’ of Wilkinson and Peach are not the highest geological subdivision of the district, either strati- eraphically or structurally. hey are earlier than, and structurally they underlie, the greater part of the Islay Quartzite, as well as the whole of the Port Ellen Phyllites and Easdale Slates. 3. In conformity with the previous paragraphs, several correlations must now be abandoned. Thus the Scarba Conglomerate is not the equivalent of the Portaskaig Conglomerate, but is of considerably later date. 4, Small-scale isoclinal folding is of less significance in the greater part of the district than has sometimes been thought. The main feature of the tectonics of Eastern Islay is a comparatively simple isoclinal anticline overthrown towards the north-west upon the Loch Skerrols Thrust. The thrust itself has been well described by Dr. Peach and Mr. Wilkinson. 5. Finally, grounds are given for believing that an accurate knowledge of the structure and rock-concession of Islay is of crucial importance in determining the tectonic plan of the West Highlands generally. : 3. January 19, 1916.—Dr. A. Smith Woodward, F.R.S., President, in the Chair. The following communication was read :— “The Physical Geography of Bournemouth.” By Henry Bury, MAAC ES S., H.G-.S. _ The curves of the plateaux in the Hampshire basin (including that of Bournemouth) show a marked relation to the main river-valleys, indicating that the latter were already in existence (though probably much less deep than now) before the plateau-gravel was deposited. On the other hand, the fact that this gravel everywhere covers the main watersheds is inconsistent with the theory of deposition on simple river-terraces, and points to widespread floods and the formation of gravel-sheets at one or more periods. Paleoliths are most frequent at low levels (below 140 feet O.D.), but occur up to 350 feet O.D., where their presence must be due either (1) to a vast accumulation of gravel in Chellean times, or (2) to channelling at later dates. Both hypotheses present difficulties. 134 Reports & Proceedings—Geologicul Society of London. The Chines along the coast of Bournemouth Bay did not originate at the cliff-edge and grow inland, as generally stated, but are the over-deepened bottoms of older and longer valleys. A similar double structure is seen in the Chines of the south-western corner of the Isle of Wight, where it is due to the destruction of part of the valley of the Yar by the sea since the deposition of the valley gravel; and it is suggested that the Bournemouth Chines are due to the breach of the Solent River by the sea at the same late period. The 140 ft. bluff, running all across Hampshire to the sea-cliff at Goodwood, is comparable with the 100 ft. terrace of the Thames, and was probably formed in an estuary in pre-Chellean times. The rate of recession of the cliffin the western part of Bournemouth Bay is estimated at about 1 foot per annum. It may be more in the eastern part, but the estimate of 3 yards per annum near Christchurch, made in the Natural History of Bournemouth, is probably much too high; and the reasons given in that volume for local variations in rate cannot be accepted. The angle of the cliffs is said to have become steeper of late years ; but this is not true of the western part of the bay, and it is desirable that the observations on which the belief rests should be published. 4. February 2, 1916.—Dr. A. Smith Woodward, F.R.S., President, in the Chair. A lecture was delivered by Richard Dixon Oldham, F.R.S., on the Support of the Himalaya. He said that it was known that the major prominences of the Earth’s surface are in some way compensated by a defect of density underlying them, with the result that they do not exert the attractive force, either in a vertical or in a horizontal direction, which should result from their mass. The Volume for 1915 of the GEOLOGICAL MAGAZINE is ready, Glee Cases for Binding may be had, price 1s. 6d. net. . . JAMES SWIFT & SON, : Manufacturers of Optical and Scientific Instruments, Contractors to all Scientific Departments of H.M. Home and Colonial and many Foreign Governments. Crands Prix, Diplomas of Honour, and Gold Medals at» London, Paris, Brussels, etc. MICROSCOPES AND OTHER INSTRUMENTS FOR ALL BRANCHES OF GEOLOGY, | MINERALOGY, © PETROLOGY. Sole Makers of the “DICK? MINERALOGICAL MICROSCOPES. Dr. A. HUTCHINSON’S UNIVERSAL CONIOMETER. University Optical Works, 81 TOTTENHAM COURT ROAD, LONDON. NOW READY. THE FLOWERING PLANTS | OF AFRICA AN ANALYTICAL KEY TO THE GENERA OF AFRICAN PHANEROGAMS. BY FR. THONNER. XVI and 640 Pages, 150 Plates, 1 Map. Cloth. Price 15s. Net. | i DULAU & CO., Ltd., 37 Soho Square, London, W. Gron. Maa., 1516. Pruare VIT. TWO LARGE OBSIDIANITES (nat. size), FROM THE RaFrFrLtes MuskuM, SINGAPORE. Weights: Fig. 1. 464 grams. (when intact). Fig. 2. 3164 grams. GEOLOGICAL MAGAZINE NEW SERIES. DECADE Vik VO. INE 7 No. IV.—APRIL, 1916. ORIGINAL ARTICLIEHS. J.—Two rarer OBsIDIANITES FROM THE RaFriEs Museum, SIncAPoRE, AND NOW IN THE GeonocicaAL Department, F.M.S. By J. B. ScRIvENOR, M.A., F.G.S. (PLATE VIL.) OME years ago I was asked to look through a collection of geological specimens in the Raffles Museum, Singapore, and found in a drawer two exceptionally large obsidianites. ‘They were not labelled, and nothing could be ascertained about their history, but an assistant in the Museum said he thought they might have come from Kelantan, a State on the east coast of the peninsula. The weights of the two obsidianites were 464 and 316°4 grams. ‘The former and larger of the two was entrusted to a local firm to cut in half, with the result seen in Pl. VII, Fig.1. The photograph, nevertheless, shows that there is a group of vesicles in the centre. The photographs, which are natural size, also show that there is nothing unusual about the surface of these specimens (Pl. VII, Fig. 2). . An analysis of a portion of the larger specimen has been carried out by Mr. C. Salter, Chemist in the Geological Department, F.M.S. In May, 1915, Dr. Mueller (Gruoz. Mae., 1915, pp. 206-11) described under the name of ‘ Tektite’ obsidianites from near Tutong, a dismal, erocodile-infested station in Borneo that I also have had the misfortune to visit, and gave an analysis by Dr. Hinden (op. cit., p. 209). The close agreement in composition of the Singapore specimen is note- worthy, and is shown in the following table (p. 146), together with some of the analyses quoted in a recent paper by Mr. C. G. Thorp (‘‘A Contribution tothe Study of Australites,” Journ. W. Australian Nat. Hist. Soc., vol. v, pp. 1-26, 1914), and others of obsidian from Iddings’ Igneous Rocks, and from a description by Dr. Prior of rocks from British Kast Africa (‘‘ A Contribution to the Petrology of British East _ Africa,’ Min. Mag., xiii, pp. 245, 247, 1903). The more important constituents only are given, and the analyses of ‘ Australites’ and ‘Moldavites’ are selected from Mr. Thorp’s paper to show the extreme ranges of silica percentage. No. 12 is described by Dr. Prior as ‘‘phonolitic obsidian” ; No. 13 as ‘‘obsidian glassy soda-rhyolite”’. The range in silica percentage in obsidianites is shown by the analysis to be large. Dr. Mueller mentions the difference in the composition of obsidianites from that of obsidians. There is certainly a marked difference compared with the U.S.A. obsidians, but when one compares them with the East African rocks, which differ chiefly in the preponderance of Na,O over K, 0, and considers that a glass DECADE VI.—VOL. III.—NO. IY. 10 146 B. Smith—Ball or Pillow-form Rocks. having the composition of some of the ‘ adamellites’ or ‘ granodiorites’ would have a composition even nearer that of the obsidianites, the chemical difference that, I gather, Dr. Mueller deems esas of the obsidianites not being of terrestrial origin, does not appear to be A stronger objection to a terrestrial origin for of great importance. these Singapore specimens is ‘their weight. Pumice from Krakatoa OBSIDIANITES. OBSIDIAN. 2, i a) Lies | British ao 5 Australites. | Billitonites. | Moldavites. U.S.A. Hast a5 3 Africa, ne = : _@)_|_Q) (8) (4) (5) (6) (7) (8) (9) (10) (@11)_}) (12) © as) Si Oo» 69-80)70-90|64- 68/77 - 72/70-92|71 - 14/77 - 69/82 - 68]75 -52)74- 52/76 - 20/64 -00/70-61 Ale Oz . |14-30/13-50/16-80|) 9-97/21-20/11-99)12-78) 9-56)14-11)13-72|13-17|10-43) 8-59 TiO,g .| 1-00) 1-00; — -86; — — = = = = == °78) -15 FeO .| 5-65) 5-47] 1-01) 3-75] 5-42) 5-29) 1-45) 1-13) -08 62 73| 3-86! 5-96 Fe, Oz . -15) -32| 6-57) -32)| 1-07) — | 2-05) — | 1-74) 1-01) -34] 6-30} 2-52 MnO .|trace|trace| -20/trace} -41} +32) — -18} — |trace| -10} -37| -34 Ca O 2-61) 2-35] 3-88) 2-40] 3-78] 2-84) 1-26) 2-06) -78| -78| . -42) 1-45) -61 MgO .| 3-20) 2-45} 2-50) 1-57) 2-61} 2-38] 1-15) 1-52) -10} -14) -19| -34) -07 NaoO .| 1-16) 1-46 trace] 1-29) 2-46) 2-45) -78| -63 3-92) 3-90) 4-31) 7-59] 6-77 KeO 1-90 2-17) 4-01) 1-96) 2-49) 2-76) 2-78) 2-28] 3-63] 4-02) 4-46) 4-59) 4-46 has floated to the east coast of the peninsula, but the idea of these obsidianites having floated to the peninsula attached to masses of pumice is precluded by the absence of any pumice of similar composition; and one cannot admit that bodies of this weight could drift in the upper atmosphere any more readily than one can admit it of arifle bullet. A cosmic origin seems the only possible explanation. II.—Bat or Prttow-Frorm StRvucTURES IN SANDSTONES.? By BERNARD SmiTH, M.A., F.G.S. fW\HE structures described below occur in monotonous and generally uninteresting type; namely in sandstones, interstratified with masses of shale and mudstone, exposed near the centre of the Berwyn Anticline in parts of Denbighshire. The necessity, however, of examining every exposure, incumbent upon the Surveyor, has led me to pay attention to detail, and especially to certain phenomena that would appear to be of world- wide occurrence in sediments of all ages. Description of the Sandstones. The sandstones are of both Llandilo and Bala age. Those of Llandilo age occur sparingly in a mass of scantily fosellinerone shales in the Llanrhaiadr- ym-Mochnant district, but become more important when followed eastward along the strike in the direction of Llansilin. In the same districts the Bala Beds are more prevalently sandy, and the strata are of a more regular character. 1 With the permission of the Director of the Geological Survey. rocks of a rather _ B. Smith—Ball or Pillow-form Rocks. 147 1. Llandilo Sandstones.—In the west thick lenticles of sandstone, or masses of alternating lenticles and shales, occur at infrequent intervals, as at Llanrhaiadr, where one bed is as much as twenty feet in thickness. Farther east the beds of sandstone appear more frequently, and are often thicker than those in the overlying Bala, and sometimes of coarser type. They are well-developed near Moel y Gwelltyn, Gyrn Moelfre, Craig-yr-hwch, and Foel Rhiwlas. The sandstones are blue laminated gritty quartz-felspathic and slightly calcareous rocks, often weathering like an ashy sediment; whilst some beds are true ‘ashy sandstones’. They contain pellets and pebbles of shale and mudstone, and in weathered specimens show brown or yellowish-red earthy inclusions. Like the Bala sandstones they contain white mica, which is clustered thickly along the ripple- marks. Although the prevalent type of rock is well-laminated, some of the coarser parts appear to be structureless. Drift- and current- bedding is fairly common. The constituent grains are angular and of two sizes, respectively about ;3>5 and 345 inch in diameter. 2. Bala Sandstones.—These occur normally as beds averaging about 2 feet in thickness, with interstratified shales and shaly sandstones. The thicker beds are nearer 3 feet across, but in some places, such as Nant Engyll Quarry, Coed Garth Eryr, Llwyn Bryn Dinas, and Llangedwyn Hall, lenticular masses, like those in the Llandilo, occur up to 10 feet in thickness. ¢ i Ra in, AG Fic. 1.—Ball and pillow-form structures in beds of sandstone between cleaved shales, in crag west of Moelfre, Llansilin. When fresh the rocks are tough, blue, or blue-grey, fine-grained laminated micaceous sandstones, with many included lamine of shale. They are fossiliferous and occasionally slightly calcareous, when they weather to rottenstone. Frequently they are ripple-marked and show drift- and current-bedding, the latter structure being most common in the more lenticular masses. They are less felspathic than the Llandilo sandstones, but contain some thin layers of ash and isolated crystals of felspar. Pillow-form and Ball Structures. In some sections, either natural or quarried, parts of the sand- stone, interbedded either in similar sandstone or in shale, assume 148 B. Smith—-Ball or Pillow-form Rocks. a pillow-form (Fig. 1), ball-like, or semi-spheroidal habit. The spherical contours are usually developed on the undersides of projecting ledges of weathered sandstone as rounded lobes and curved surfaces, whilst occasionally they occur on the upper surfaces as well, when the rock becomes still more pillow-form in appearance. The spheroids are hardly ever completely developed. If they were they would average about 1 foot in diameter, with a maximum of 2 ft. 6in. The pillow-form shapes are sometimes arranged parallel to the bed,’ but are frequently inclined. They are often twice as long as thick, and average from one to two feet in length. Externally the shapes of these masses recalled those of pillow- lavas, or the spheroidal weathering of dolerite, and since some of the pillows contained much felspathic material and some of the spheroids appeared to be due to weathering, their occurrence was sufficiently interesting to warrant further investigation, which showed that they were of two kinds. aN \ WN be ee LAA Wits iN vi ‘ Fig. 2.—Shell-jointing in sandstone. Two Types of Structure. 1. Structures due to jointing and weathering (shell-jointing). 2. Pillow-form or ball structures due to internal build. 1. Where the rocks are evenly bedded and well jointed the corners of roughly rectangular masses, blocked out by joints and planes of stratification, are liable to shell off in layers roughly concentric with the central portions of the blocks. As in dolerite the shell structure may be due primarily to shrinkage. In undoubted cases (Fig. 2 where this shelling off takes place ' the fracture was unrelated to the lamination, which runs normally through the pillow. The exposed top corners of a block are usually shelled off first, unless the lower corners project prominently from the underlying beds. On hammering at such a pillow the concentric weathered shells may be knocked off in turn until only the tough unweathered core remains. 2. In other cases, if we hammer at a pillow or spheroidal mass we discover that its internal structure may correspond with its curved face; that is to say, the lamine of sandstone are curved in conformity with the outer curve of the pillow. A good example occurs in an old quarry in Llwyn Bryn Dinas Wood, about one mile west of Llangedwyn. Some of the sandstone strata are evenly bedded and 1 For this reason the rock is unsuitable for use in the exposed corners and angles of buildings. It is known locally as ‘ grinsel’. ee ee B. Smth—Ball or Pillow-form Rocks. 149 apparently quite undisturbed, whilst others (Fig. 3) have ball structures strongly developed and exposed chiefly, be it noted, on their under surfaces. Where these surfaces curve upwards until they are nearly, or more than, at right angles to the normal plane of stratification, the sandstone laminz curve upwards and over, in conformity with them. In one or two places shales are plastered against the curved surfaces as if squeezed into spaces between the spheroids. a SE ee a Zz YN gl Fic. 3.—Ball structures in sandstone, Llwyn Bryn Dinas Wood, Llangedwyn. This example seemed to furnish conclusive evidence in favour of the balls or spheroids being due to internal concentric lamination, yet the next time I came across semi-spheroidal masses their curved surfaces tre +--> Ll | q--s--+~--- A N oa 3.8. Fie. 4.—Sandstone ‘ ball’, Tyddyn-main, Llansilin. were due, quite as conclusively, to jointing and weathering. How- ever, many cases of the real thing were quickly forthcoming, and T have since found that true ball structures are quite as common as, if not more common than, the rounded masses due to shelling. 150 B. Smith—Ball or Pillow-form Rocks. Other examples occurred (i) in a quarry between the road and river east of Coed Fron-fraith; (ii) in a quarry about 200 yards west of Tyddyn-main; (ili) in a quarry at l'yn-y-ffridd in ashy sandstone, where shales are pinched in between two balls; (iv) on Moel y Gwelltyn, where the balls are from 18 inches to 2 feet in thickness ; (v) in the crags west of, and overlooking, Moelfre (Fig. 1); (vi) in a quarry south of Pant-er-eos-uchaf; (vil) in numerous quarries and crags between Moelfre Hall and Moeliwrch on Gyrn Moelfre. In some cases it is possible to study sections of the ball structures on joint faces where the lamination has been rendered visible by weathering. In a quarry about 200 yards west of Tyddyn-main (ii above, Fig. 4) a flat broken surface of a ball, in a big lenticle of sandstone, reveals its internal structure, for the exposed lamine are curved back upon themselves in a sharp fold, to which the outer curve of the ball conforms. ~ ome) \ S the 1 a ah z es —--------~-— > a) Fic. 5.—-Contorted layers in sandstone near Pentre, Llansilin. A better section is visible in an old quarry in a wood 200 yards east of Pentre, on a nearly vertical joint face which runs approxi- mately in the direction of the dip (Fig. 5). It shows a well-laminated and slightly drift-bedded sandstone, in which some of the laminze (about 12-15 to the inch) are strongly contorted, folded back upon themselves, and cut off from other parts of the rock by faults. The rounded ends of these curved masses are often buried in apparently structureless sandstone, whilst the disturbed horizon is both underlain and overlain by normally bedded sandstone. At some future date the balls will be developed by differential weathering of the structureless parts of the rock. B. Smith—Ball or Pillow-form Rocks. 151 Cause of Contortion. Anything more unlike concretionary action could hardly be imagined. To what, then, must these structures be attributed ? ’ TIT can imagine no means that would avail to turn over, and break up, layers of sediment on this scale—sandwiched between normally bedded identical layers of identically similar sandstone‘—after the higher layers had been deposited. Movements during consolidation, due to differences in composition, cannot be invoked, because there is _ no difference in composition. Nor can we appeal to cleavage-stresses, although in some cases, discussed below, they may have achieved something of a secondary order. There remains to find some means whereby the sediment could have been disturbed before the higher undisturbed layers were deposited. Two agencies are possible: either (1) packing or sliding movements on gentle slopes owing to irregularity of deposition and gravitational -ereep, or (2) movements of overlying bodies of water as tidal or ocean currents. Nature of the Movements. The highly lenticular character of these beds has already been emphasized, and the examples figured show how the rock was drift- bedded and ripple-marked during deposition. Nothing is more obvious than that the sediment was transported by currents and laid down sporadically in fairly shallow water, layers of mud being frequently interspersed between layers of sand and silt. From these facts we may safely infer that the sea-bed was gently undulating. Again, the sediments were apparently formed off the shores of volcanic islands drained by rivers carrying ashy and other sediment to the sea, which would be agitated periodically by strong tidal currents. The large voleanic bombs and lumps of shale in the Bala ashes would seem to prove that the volcanoes rose above the water, for the bombs could not have been cast far from the vents had the latter been submarine. Most of the sediment had apparently reached a state of pasty semi- consolidation that allowed of overfolding and thrusting within its mass, but its upper layers were still so incoherent that they could be stirred up and easily rendered structureless. A lenticle of sandstone, deposited on a gentle slope, might find itself in a state of unstable equilibrium through gravitation alone, which would set up a tendency to creep and internal readjustment. Furthermore, the edges of a lenticle deposited on a slope of mud would tend to break up and have its detached fragments incorporated in the enveloping mud. It is well-known how Glacial and post-Glacial gravels, resting on gentle inclines, have become contorted by gravitational creep. A mass of laminated sandstone under water would be an even more likely subject for this operation, which might be started or accentuated by tidal movements, or the sweep of changeable ocean currents. 1 Contrast ‘ mud-lumps’, where mud is squeezed out from between sand- stones that are of different composition and grade of material (see later, p. 155). 152 B. Smith—Ball or Pillow-form Rocks. Current Action. The disturbing effects of current-action can indeed be demonstrated ; for semi-rounded lumps of sandstone (1-2inches across, in Llwyn Bryn Dinas Wood) occur in the shales lying between the thicker lenticles of sandstone, as if thin layers had been deposited and subsequently broken up, rolled along, and embedded in the mud. Conversely, the thicker sandstones contain little strips, angular pellets, or rounded pebbles of mudstone—proving without doubt that the beds were frequently torn up when they had barely attained a state of consolidation. We may compare such destructive current-action with that to which I ascribe the contortions in the dolomitic sandstones in the Keuper Marl of Nottinghamshire.’ In this connexion also, the occurrence of structureless sandstone in which the balls or pillows are embedded is suggestive. Thus, although I am not an advocate of the efficacy of current- action to form the large ball structures met with in these Paleozoic sandstones, but prefer to think they are chiefly due to gravitational creep in lenticular beds, I am of the opinion that currents have played a greater part in aiding such movements than some geologists might admit. Effects of Cleavage. The effects of cleavage may now be considered. During the process of shearing and compression that induced cleavage the irregular lenticles of sandstone acted as resistant cores or sheets, and only yielded to the impressed forces after a struggle. In some cases they slid bodily through the shales, which were caused to flow round them like so much butter; in other cases they were bent and folded ; whilst in others, again, they were faulted or broken into small masses—like the quartz veins in the Ilfracombe slates. The latter condition is so common that it is inadvisable to rely upon a dip taken in any small isolated mass of banded sandstone, for I have frequently found the true dip of the enclosing shales to be almost at mght angles to that of the broken lenticle. When the sandstones occur as large lenticles or clusters, the boundaries of the mass, or group, are often faulted, and the combination buckled into folds—structures which may be further complicated by post-cleavage movements. The shaly portions of the combination are frequently cleaved, whilst at other times the sandstones are cleaved as well. In the latter case the angle of cleavage in the sandstones is invariably higher than it is in the shales: an effect that would seem to imply that the thickness of the shale-belts, relative to that of the sandstones, has been decreased by cleavage-shear, and that the higher beds of sandstone have moved further than those below. In the heart of a thick mass of sandstone cleavage has had little or no effect upon the relations of the ball structures to their surroundings ; but where they occur at the margin of a lenticle (a very likely position) and where lumps of sandstone in the first instance have been detached 1 “The Upper Keuper Sandstones of East Nottinghamshire ’’?: GEOL. MAG., 1910, pp. 302-11. i B. Smith—Ball or Pillow-form Rocks. 153 and isolated in the shales, the effect of the cleavage has been to jam these lenticle-noses or semi-rounded balls into the shales, which were thereby slickensided and plastered tightly upon them. Insome cases, indeed, a sort of subsidiary cleavage (due to jamming) curves round the balls in places where the ordinary cleavage had little effect. Fic. 6.—Diagram showing curved cleavage. A local curved cleavage, developed in this definite manner, may either accentuate the true ball structures, or suggest ball structures even when the sandstone lamine do not conform to the curved surface. Fig. 6 is an attempt to express these two cases diagrammatically. Similar effects are liable to occur also on a large scale about masses of sandstone and shale 100—200 feet in thickness, the slickensides being represented by faults. In the lee of the mass we may find (taking the analogy from a ‘rain-shadow’) a ‘cleavage-shadow ’, or locality in which the cleavage is modified or absent owing to the protection afforded by the sandstone. Some allied phenomena. Amongst allied phenomena we might instance the contortions and uneven deposition of some of the Wenlock—Ludlow beds of Denbigh- shire. These consist chiefly of blue shales with sandy laminz which become clustered at frequent intervals to form sandy shales or thin beds of sandstone. The clusters are usually only half an inch or so in thickness, but some of the sandy beds may attain a maximum of 6-8 inches. Occasionally the sandy beds are split up by muddy Se * ee ee a ree € Ins Se Fic. 7.—Folded layers of sandstone and shale, Pant-yr-onn, Llanelidan. layers. In one case, near Pant-yr-onn, Llanelidan, an 8 in. band of laminated sandstone contained 6-7 muddy layers, those near the centre of the bed being thrown into gentle undulations, of wave- length about 9 inches and amplitude about 3 inches, whilst the upper and lower layers pursue a straight course (Fig. 7). Here and there the folded bands of mudstone thicken quite suddenly, especially on 154 B. Smith—Ball or Pillow-form Rocks. the crests of the small anticlines. Had the folding been due to packing caused by cleavage-stresses the whole bed would have folded, instead of only the middle portion. The most likely explanation to account for the facts is that the composite bed was deposited on a slight slope, and a creeping movement was set up, whilst the layers were still soft, causing the bed to become undulose internally, and to thicken at the same time. The top and bottom of the bed would remain relatively undisturbed, but each individual layer of sandstone, between the little layers of mud in the middle of the group, would move slightly in the direction of the creep. Signs of current-action and uneven deposition are common in these beds. In the quarry south-south-west of Nant Gaer, near Bryn Eglwys, there is a 6in. band of slightly calcareous and fossiliferous laminated sandstone with uneven upper and lower surfaces. The upper has flowing curves which correspond roughly with the surfaces of the ripple-marks, whilst the lower is much more irregular, for the sandstone fills up little pockets that either have been torn out of the mud by current-action, or have been formed by the lowest sand- stone lamin buckling downwards whilst in a pasty state. ‘The higher rippled lamine of sandstone truncate this lower pocket-filling set (Fig. 8). Fig. 8.—Sandstone in shale, Nant Gaer, near Bryn, Kglwys. Most of this effect, as in the case of the Keuper ‘skerries’ of Nottinghamshire, I should attribute to current-action,’ for the wave- length and amplitude of the ripples agree very closely with those proper for sandstones of this type, as worked out by Sorby.? The occurrence is altogether different from that shown in Fig. 7. Conclusion. Ball or pillow-form structures in sandstones, and certain bucklings and foldings, seem to be most satisfactorily explained on the assumption that they are primarily due to internal readjustments of freshly and unevenly deposited sediments, acting mainly under gravitation. These readjustments may be aided, or started, by the action of strong currents. The above-mentioned structures and their attendant phenomena are not confined to Paleozoic sandstones,* but must occur frequently in 1 “The Upper Keuper Sandstones of Hast Nottinghamshire ’’: GEOL. MAG., 1910, pp. 306-7. 2 “On the application of Quantitative Methods to the Study of Rocks’’: Q.J.G.S., vol. lxiv, pp. 171-233, 1908. * I have recently seen ball structures in the sandstone of St. Bees Head, Cumberland, and Dr. R. lL. Sherlock tells me that pillow-form masses of Magnesian Limestone overlie puckered Marl Slate in a cutting at the north end of Annesley Tunnel in Nottinghamshire. 3 . » - aa 8 ee EE B. Snuth—Ball or Pillow-form Rocks. 155 the Mesozoic and Tertiary rocks, especially the latter. I am not aware, however, that much attention has been paid to them, although I am convinced that a strict examination of ripple-marks, current- and drift-bedding, internal creeping-movements, and removal of sediment by current-action would yield important results if studied in conjunction with present-day sedimentation in, and beyond, the mouth of one of our great tidal estuaries. We want to know, for example, the extreme depth at which ripple- marks can be formed, and to what extent depth is a deciding factor. We require reliable data as to the rate at which sandy sediment may be accumulated and again removed by current-action; the relative effects of a flood- and ebb-tide on sedimentation; and if a layer of drift- or current-bedded sand is laid down by the one, how far it may be wiped out by the other, or covered up by further sediment. When we find the lamin of false-bedding or ripple-drift (in a rock exposure) dipping in a certain direction, are we to assume that the sediment was carried directly to that spot from the land? These and similar questions may be difficult to solve, but would give scope to an investigator provided with a suitable boat, and ample leisure for the task. Tae Misstsstppr Detra. Since writing the above it has been my good fortune to light upon an instructive paper dealing with the conditions obtaining in the region of the Mississippi Delta.' Investigations were undertaken with the object of discovering the nature and mode of formation of the mud-lumps that obstruct the navigation at the river mouths. The results achieved, although they have not fully settled the origin of the mud-lumps, are enlightening. It has been shown, for example, that the deposits near the mouth of the river consist of lenticular layers of dark-blue clay, fine sand, and silt, and a great many beds of intermediate character, each of which grades into the adjacent beds. The sandy beds, and those of mixed sand and clay, are much more rigid than nearly pure clay. The most rigid material is a mixture of sand and clay in certain definite proportions, whilst some of the clays are very fluid. The resemblance between these deposits and some of those of Ordovician and Silurian age, as they would have been at the time of their formation, is striking; although this, of course, does not imply that the Lower Palzeozoic deposits were of deltaic origin. Just off-shore, and adjacent to the mouths of the river, silt is accumulating at the rate of several inches a year, and the character of the deposit varies from season to season. uring high-water—the first half of the year—the sediment is coarser than during the low- water period. The apparent result is astructure somewhat resembling the annual rings of growth of trees. This is a suggestive fact, if we bear in mind the sequence of sedimentation of some of the older rocks, in e.g. the Wenlock—Ludlow Series (see p. 153). Again, certain features of the Delta suggest that it is affected by a process of bodily flowage towards the sea, giving rise to readjustment 1 The mud-lumps at the mouths of the Mississippi, by E. W. Shaw, U.S.G.S., Professional Paper 85-8, 1913. 156 Dr. C. 8. Du Riche Preller—Prietre Verdi. between the more or less resistant layers of sediment, both in the Delta itself and in the sea-bottom just off-shore.! The surface of the deltaic deposits is also subsiding, the subsidence being most rapid where the Delta is growing most rapidly; and the material is presumably becoming more compact and losing its very watery condition. These, again, are significant facts, and bear directly upon the subject of this communication. We have at once a clue to much that was pure surmise—the unstable relations of these sandy, silty, and clayey deposits to one another, and the comparative rigidity of some of the more sandy beds, which would allow of thrusting and buckling within them, although they were still in a pasty condition. Il].—Taue “ Prerre Verpr’’ or tHE PifmMontrEsE ALPS. By C. S. Du RIcHE PRELLER, M.A., Ph.D., M.I.E.E., F.G.S8., F.R.S.H. N a previous paper on the Permian Formation in the Alps of Piémont, Dauphiné, and Savoy,? I referred incidentally to the large masses of pietre verdi or greenstones which constitute perhaps the most striking geological feature of the extensive areas covered by the crystalline rocks of the Piémontese Alps in a crescent-shaped curve about 200 miles in length from the Maritime range to Monte Viso, Grand Paradiso, and Monte Rosa. In the present paper I propose to deal more fully, although necessarily within narrow limits, with these pietre verdi which, owing alike to their extraordinary development, variety, and complexity, to their intimate association with each other and with the crystalline sedimentary rocks, and to their intricate composition and origin, have for the last fifty years presented most interesting problems and passed through many remarkable phases of interpretation. As a necessary preliminary to a description of the different areas, it will be convenient to briefly consider the most recent classification of the crystalline formations of the Piémontese Alps generally, and of the pietre verdi rocks in particular. I. CLAssIFICATION OF THE CRYSTALLINE FoRMATIONS. In a short paragraph of the previous paper already quoted, I outlined the sequence of the crystalline rocks of the Piémontese Alps as evolved by Zaccagna in his revealing memoirs of 1887 and 1892.8 In this classification he retained Gastaldi’s two principal pre-Paleozoic zones or horizons,‘ but with this essential difference, that for Gastaldi’s upper or so-called pietre verdi zone he substituted 1 The mud in the ‘lumps’ is supposed to be squeezed out from between the sandy beds. 2 GEOL. MAG., January, 1916, p. 7; ibid., p. 15. 3D. Zaccagna, ‘Studi geol. sulle Alpi Occid.’’: Boll. R. Com. geol. d’It., 1887, p. 346 et seq. ‘‘Riassunto di Osserv. sul Versante Occid. Alpi Graje’’: ibid., 1892, p. 175 et seq. 4 B. Gastaldi, ‘‘ Studi geol. sulle Alpi Occid.’’?: Mem. R..Com. geol. d’It., 1871, vol. i, p. 3 et seq. ‘‘ Spaccato geol. lungo le valli sup. Po e Varaita’’ : Boll. R. Com. geol., 1876, p. 104 et seq. Dr. C.S. Dw Riche Preller—Pietre Verdi. 157 the mica-and-cale schist zone with pietre verdi as associated rocks, the latter being, in point of superficial area, a subordinate, the former the predominant part of the whole formation. Zaccagna’s two Archean zones thus comprised: (1) a lower one, restricted exclusively to primitive gneiss and granite without pietre verdi; and (2) an upper one, graduating, in ascending order, from minute and tabular gneiss to mica-schists and cale-schists, each group with crystalline limestone and pietre verdi. This classification, in its logical sequence and convincing simplicity, received the imprimatur of the Italian Geological Survey under its eminent Director, the late Comm. F. Giordano,’ and was also accepted by the French Survey, by Bertrand, Termier, and other French geologists. It derived additional force from the more intense metamorphism and crystallinity, pro- gressing from west to east, of the rocks on the Piémontese as compared with those on the French side of the Western Alps; and this, together with the fact that until then, about 1890, no deter- minable fossils had been found even in the uppermost calc-schist horizon, warranted the entire crystalline series of Piémont being classed as of pre-Carboniferous, and, in the absence of the lower Paleozoic, of Archean age. But in 1894 Bertrand returned to his former view of the Mesozoic age of the schistes lustrés which, in opposition to the late Professor Lory’s Triassic and to Zaccagna’s Archean views, he and Termier had already pronounced Liassic in the well-known case of Mont Jovet in Tarantaise (Isére Valley). In his Etudes dans les Alpes Frangaises * Bertrand maintained the Liassic age of the calc-schists not only on the French but also on the Italian side, on the ground that lower Triassic masses frequently underlie the calc-schists. Even before the publication of that work, Professor Parona, of Turin, had discovered Radiolaria in the silico-calcareous mass associated with the cale-schists and pietre verdi (serpentine) of Mont Cruzeau, near Cesana,* a discovery followed a few years later by other evidence of characteristic Liassic, Rhetian, and Triassic fossils in the dolomitic and caleareous masses which, in the lower as well as in the upper valleys of both Southern and Northern Piémont, occur at varying levels of the cale-schist horizon, either resting on, or intercalated between, or in some cases at the base of, the crystalline calc-schist strata. These discoveries were due chiefly to the untiring industry and perseverance of Franchi, who, in two important memoirs of 1898 and 1904,° claimed to have established the Mesozoic, 1 Boll. R. Com. geol., 1887, pp. 342-5. 2p. Termier, ‘‘ Sur le Permien du massif de la Vanoise’’: Bull. Soc. géol. France, vol. xxi, p. 124 et seq., 1893. 3 M. Bertrand, Bull. Soc. géol. France, vol. xxii, p. 69 et seq., 1894. “cC. F. Parona, ‘‘Sugli Scisti silicei a radiolarie di Cesana presso il Monginevra’’: Atti R. Ace. Sc. Torino, vol. xxvii, 17. Gennajo, 1892; also noticed in Davies & Gregory’s paper on ‘‘ The Geology of Mont Chaberton ’’, Q.J.G.S., 1894, p. 303 et seq. ° §. Franchi, ‘‘ Sull’ et& mesozoica della zona delle pietre verdi nelle Alpi Occidentali’’: Boll. R. Com. geol., 1898, pp. 173, 325 et seq. ‘‘ Ancora sull’eta mesozoica, etce.’’: ibid., p. 125 et seq. Franchi, Novarese, and Stella were in charge of the detailed survey of the Piémontese Alps forthe new1:100,000 map in 158 Dr. CO. S. Du Riche Preller—Pretre Verdi. and more especially the predominantly Liassic, age of the cale-schist formation, including in the same the pietre verdi as associated rocks. He thus assimilated the age of that formation and that of the schistes lustrés in accordance with Bertrand’s views, with which he is thoroughly imbued and which, since Bertrand’s death, have been upheld and even carried considerably further by Termier. Franchi’s memoirs and his evolution from the Archean to the Mesozoic led to a controversy as interesting as it was vigorous and protracted, between Zaccagna and himself, not as to the facts, which were not in dispute, but as to the interpretation of the same. ‘'o Franchi’s contention Zaccagna' opposed, on stratigraphical grounds, his own explanation that the fossiliferous calcareous and dolomitic deposits occur in eroded gaps and as squeezed wedges (przsicature) in the crystalline cale-schists, in which they were infolded by dynamic action, in certain cases by displacements due to local overthrusts, and that as such they are quite distinct from the true cale-schists, whose pre-Palwozoic age he therefore strenuously reaffirmed.2? In the result Professor Taramelli, of Pavia, and Professor Parona, of Turin, as referees appointed by the Geological Survey, recommended, in their reasoned report of 1911,° that for the purposes of the new large-scale map 1: 100,000 of the Piémontese Alps, Franchi’s interpretation, as being, in their view, more con- vincing and up-to-date, should be adopted, but with the explicit and judicious reservation that the question cannot be considered settled but remains open; that at a lower horizon there may be cale-schists conjunction with Mattirolo, who supported Zaccagna’s interpretation. Franchi published in Boll. R. Com. geol., 1909, p. 252, a forty-page reference of the literature on the crystalline schists from Gastaldi (1871) downwards. The principal localities which yielded Triassic and Liassic fossils in the calcareous and dolomitic masses of the calc-schist horizon are the Grana, Narbone, Maira, Elva, and Varaita Valleys in Southern Piémont; Chianoc in the lower, and Rocca d’Ambin, Gad d’Oulx, and Bardonecchia in the upper Susa Valley; Villeneuve in the upper Aosta Valley, and the Col du Petit St. Bernard, all in Northern Piémont. The fossils, most of which were determined by Professor Di Stefano and Professor Canavari, include, among others, Radiolaria, Belemnites, Arietites, Crinoids, Hncrinus, Pleurotomaria, Avicula, Corallari, Gyropelle, Pentacrinus, Phylloceras, etc. 1D. Zaceagna, ‘‘Osservazioni sugli ultimi lavori intorno alle Alpi Occidentali’’: Boll. Com. geol., 1901, pp. 4, 129; 1902, p. 149; 1903, p. 297. 2 Zaccagna’s interpretation agrees with Professor Bonney’s view that nothing is more common in the Alps than Jurassic and Triassic wedges in the crystalline schists. ‘‘ Mesozoic Rocks and Crystalline Schists in the Lepontine Alps’’: Q.J.G.S., 1894, p. 285; also ibid., p. 277. Baretti (Studi Gran Paradiso, etc., 1876-7) also considered the French calc-schists the upper and the Piémontese calc-schists as the lower crystalline formation. 3'T. Taramelli and C. F. Parona, ‘‘ Relazione sull’et& da assegnarsi alla zona delle pietre verdi nella Carta geol. delle Alpi Occidentali’’: Boll. R. Com. geol., 1911, pp. x-xxiv. The controversy between Franchi and Zaccagna turned more especially on the great calc-schist area extending from the Gesso Valley in Southern Piémont parallel to the Franco-Italian frontier to the Susa and Aosta Valleys towards Monte Rosa. ‘The smaller, isolated area of Courmayeur, running parallel to Mont Blanc, was recognized as Liassic and Triassic, and was, therefore, not in dispute. Dr. 0. S. Du Riche Preller—Pietre Verdi. 159 in Zaccagna’s sense; and that the Piémontese Alps, in their elusive complexity, may J vet reveal the most sur prising phenomena just when the problem of the crystalline schists and pietre verdi appears to have _been solved. Thus, in the most recent Italian Geological Survey map 1: 100,000, as also in the one of 1 : 400,000 of 1904, the Piémontese cale-schist formation has been rejuvenated as equivalent to and contemporaneous with the schistes lustrés of the French, the Biindnerschiefer of the Swiss, and the Schieferhiille of the Austrian Alps. It figures,. therefore, as the Liassic—T'riassic crystalline ‘‘ Piémontese”’ facies, with two subordinate facies—the ‘‘ mixed ”’ and the “‘ ordinary ”’ Trias. This rejuvenation, which is practically a reversion, mutatis mutandis, to Sismonda’s ‘‘ metamorphosed Jurassic schists ” of the early ’ sixties, entailed a similar stratigraphical process as regards the mica-schists and the minute, tabular, and graphitic gneisses which, accordingly, are now assigned to the Permo-Carboniferous, corresponding to Bertrand’s and Termier’s ‘‘série cristallophylienne permo-carbonifére’”’. The only formation left to the Pre-Carboniferous (or Pre- Paleozoic) is therefore that of the primitive gneiss belt of the Mercantour, Maira-Dora, and Gran Paradiso massifs, which formation constitutes the practically undisturbed substratum of all the more recent series.! This primitive gneiss, often of granitoid and porphyroid structure with large felspar crystals up to 8 centimetres in length, differs lithologically from the more recent minute and tabular gneiss, chiefly in that the small-grained elements of the latter are conspicuously rich in quartz and predominantly white mica. As regards the calc- schists, they are composed prevalently of calcite, aggregations of quartz in minute granules, and with white or greenish mica, the rock being generally of grey and often blackish colour due to a carbonaceous pigment, with numerous minute crystals of pyrite and other metallic minerals. When this typical cale-schist is deficient in calcite or loses it altogether, it assumes an essentially phyllitic character; when, on the other hand, calcite predominates over the other minerals, the calc-schist. becomes micaceous crystalline limestone or ‘calcefiro’?; and when the crystalline limestone is, by contact, impregnated with serpentinous matter, it becomes ‘ophicalce’, as e.g. the green marble of Susa. 1 The official geological map of France, 1: 1,000,000, published in 1904, which extends to the Italian side as far as the Po Valley, includes in the Permo-Carboniferous not only the minute and tabular gneiss and mica-schists, but also the primitive gneiss belt, for which there is no warrant. Similarly, Termier (‘‘ Les schistes cristallins des Alpes occidentales,’’ Comptes Rendus du Congrés géol. Vienne, 1913) embraces in his série cristallo-phylienne triassique compréhensive all the younger formations down to the Eocene inclusive. Both cases are ultra-synthetic, and are not accepted by the Italian Survey. Professor Gregory’s view that the gneisses which he terms Waldensian (Q.J.G.S., 1894, p. 232 et seq.) are Pliocene and intrusive runs counter to the accepted interpretation of the coarse-grained gneiss being the primitive, viz. ‘fundamental’, substratum of the Cottian and Grajan Alps. Professor Gregory’s conclusions are traversed also by Novarese, ‘‘ Rilevamento geol. Valle Germanesca (Alpi Cozie), 1894,’’ Boll. R. Com. geol., 1895, p. 277 et seq., and Franchi, ibid., 1897, p. 13 et seq. 160 Dr. C. 8S. Du Riche Preller—Pietre Verdi. The new classification, besides harmonizing with the most recent interpretations west and north of the Alps, has the signal advantage of having eliminated Gastaldi’s ‘‘ pietre verdi zone”, which, in his separate and far too comprehensive sense, had become a fruitful source of misconception. As experience has shown, pietre verdi are not peculiar to any particular horizon, and throughout Italy, as elsewhere, occur in all the formations from the Hocene down to the Paleozoic; in the Piémontese Alps, though in a special form, even in the primitive gneiss. II. CLAssIFICATION OF THE PIETRE VERDI. In order to avoid tedious repetition, it will be convenient to specify briefly the leading varieties of the pietre verdi, some of which have characteristics peculiar to the Piémontese Alps. Gastaldi, with his wonderful intuition and perspicacity, laid down certain broad lithological distinctions which, in the main, are still correct. They were used by hisimmediate contemporary followers Striiver and Baretti, and after them by Bucca,’ in their excellent and diffuse macroscopic and microscopic investigations, and until recently also by Zaccagna and Mattirolo; but the results of the detailed survey and the consequent extension of microscopic work, notably by Franchi, Novarese, and Stella, have led to revised and more precise definitions, more especially in reference to the amphibolic and prasinitic series which Gastaldi included indiscriminately in his ‘amphibolic’ or ‘“magnesian schist zone’. On the rational ground that not amphibole, i.e. hornblende, but triclinic felspar is the most prevalent constituent of pietre verdi, the revised nomenclature divides all the basic rocks of the Piémontese Alps into three groups on a felspathic basis, viz. rocks in which felspar, as a constituent element, is essential, subordinate, or absent. In the following table I have enumerated only the principal, most diffused rocks, without their schists, their infinite graduations, and their often overlapping varieties and combinations.’ . PIETRE VERDI ROCKS. I. Rocks with primitive elements. (1) Essential. Diorite, diabase, porphyrite, gabbro, and their FELSPAR varieties. (2) Subordinate. Felspathic lherzolite, felspathic hornblendite. (3) Absent. Lherzolite and peridotite, hornblendite. 1 G. Striiver, ‘‘Cenni sui graniti massicci delle Alpi Piémontesi e sui minerali delle valli di Lanzo’’: Mem. descr. Carta geol. d’Italia, 1871, p. 37 ef seq. M. Baretti, ‘‘ Studi geol. sul gruppo del Gran Paradiso’’?: Mem. Acc. Lincei Torino, vol. i, p. 197 et seq., 1876-7. L. Bucca, “‘ Appunti petrogr. sul gruppo del Gran Paradiso’’: Boll. R. Com. geol., 1886, p. 449 eti seq. 2 The table is founded on the nomenclature worked out by Novarese and Franchi, Boll. R. Com. geol., 1895, p. 164 et seq. and p. 181 et seq.; but I have arranged it somewhat differently so as to group the rocks with primitive and those with secondary elements separately and more prominently. Dr. 0. 8. Du Riche Preller—Pietre Verdi. 161 II. Rocks with secondary elements. (1) Essential. (a) Prasinite group: with a dominant non- felspathic element, viz. chloritic, amphi- bolic (actinolite and glaucophane), or epidotic prasinite, and varieties. (6) Euphodite and its varieties. (2) Subordinate. (a) Amphibolite group: felspathic and epidotic amphibolite with frequent glaucophane. (6) Epidotites and zoisitites, felspathic. (a) Amphibolite group: epidotic and garnetiferous amphibolite with dominant glaucophane, eclogite. (6) Epidotite, zoisitite. (c) Serpentine, serpentinous, chloritic, and talcose schist. FELSPAR (3) Absent. It will be seen that the old generic group of amphibolites or hornblendic rocks is separated into amphibolites proper and prasinites, the last-named designation having been adopted from Kalkowsky and Zirkel as basic rocks or ‘Griineschiefer’ of a felspathic basis with chlorite, hornblende (the bright-green actinolite or the bluish-green or violet fibrous glaucophane) and epidote, one of these being dominant as a non-felspathic element. The amphibolites, largely derived from diorite and composed of albite, epidote, and dominant amphibole, are mostly compact, passing to schistose, although the hardest, massive amphibolite, viz. ‘hornblendite’ or ‘ Hornblendefels’, is, in large masses, comparatively rare in the Piémontese Alps. The prasinites, on the other hand, are on the whole less compact and more often schistose, and in the main, like the amphibolites, altered, transformed, or metamorphosed from massive eruptive rocks. They often contain, as an accessory mineral, white mica, but rarely biotite, and include, as a largely diffused variety, the chloritic rock ‘ovardite’, first recognized and so named by Striiver’ from Torre d@Ovarda, a ridge in one of the three Stura di Lanzo valleys. It is composed of epidote, microscopic amphibole, and predominant chlorite in a plagioclase groundmass. Amphibolic schist, the equivalent of ‘ Hornblendeschiefer’, is intermediate between amphibolites proper and prasinites.? A further distinction made is that between gabbro and euphodite in the sense that gabbro is restricted to the primary eruptive rock with its elements unaltered, while in euphodite the triclinic felspar is already altered to saussurite and the diallage to smaragdite—the latter being, like epidote and the amphibole varieties, a largely diffused mineral in the Piémontese Alps. Again, massive serpentine, as the direct product of altered lherzolite and peridotite, is distinct serpentine schist, which is a further 1 Striiver, Una Salita alle Torre d’Ovarda, Torino, 1873, and Bucca, loc. cit., 1886, p. 453. 2 The felspar-actinolitic rock noticed by Professor Bonney near Fenestrelle in the Chisone Valley (‘‘ Two Traverses of the Crystalline Rocks of the Alps”’ : Q.J.G.S., 1889, p. 80 et seq.) is an amphibolic prasinite, viz. ovardite, while the schist with glaucophane, the epidiorite, and the dark-green porphyrite mentioned by Professor Gregory in his ‘‘ Waldensian Gneisses’’, loc. cit., come under the category of prasinites (ovardites) and amphibolites. DECADE VI.—VOL. III.—NO. IY. 11 162 Dr. C. S. Du Riche Preller—Pretre Verdt. stage of alteration, and still more from serpentinous schist, which, occurring frequently as intermediate between crystalline schists or, again, between crystalline limestone and pietre verdi, is the product of chloritic decomposition of the latter. As such it may, by the abstraction of magnesia, be derived from any of the basic rocks with altered elements, notably from euphodite, amphibolite, and prasinite, or their schists, although the prototypes of these rocks—gabbro, diorite, and diabase—hayve, apparently, no identity of origin or affinity with serpentine proper. So-called serpentinous schist is therefore pseudo-serpentine, and represents, together with chloritic and talcose schist, probably the last stage of alteration and metamorphism, not only of serpentine but of some of the other pietre verdi series, The rocks with altered elements often assume a laminated, gneissi- ' form structure, and exhibit a marked affinity with gneiss or, again, with mica-schists and even with calc-schists. Thus minute eneiss becomes amphibolic, prasinitic, or epidotic ; mica-schist becomes epidotic and even more frequently glaucophanic when in association with the blue glaucophane or gastaldite variety; while ovardite, when very rich in chlorite and taking up mica, quartz, and calcite, passes into prasinitic cale-schist and phyllite. The massive eruptive rocks with primitive elements—diorite, diabase, gabbro, pyroxenic-biotitic porphyrite (Gastaldi’s melaphyre), and the enormous peridotitic masses—occur more especially in the gneiss and mica-schist area of Northern Piémont, that is, in the so-called dioritic belt or ‘Ivrea zone’ which extends from the eastern spurs of the valleys converging near Avigliana, west of Turin, to the Lanzo spurs, and thence north-east to Ivrea, Biella, and the Sesia valley, and beyond the latter to the Strona valley near Lake Orta. The same ‘Ivrea zone’ also extends into the Aosta valley and the valleys descending from Monte Rosa. The amphibolic, prasinitic, euphoditic, and serpentinous series with secondary elements, on the other hand, predominate in the cale-schist and mica-schist area from the upper Lanzo valleys south to Monte Viso and the Maritime Alps, and extend into the Permian and Triassic formations of the latter. The considerable euphoditic and diabasic masses of the Grana and Maira valleys south of Monte Viso are all more or less profoundly metamorphosed to epidotic (zoisitic), amphibolic, and prasinitic rocks,* and therefore do not belong to the category of eruptive rocks with. primitive elements. The constant and intimate association of the pietre verdi not only with each other but with the stratified mica- and cale-schists led Gastaldi, as previously stated, to regard all those rocks, with the only exception of the primary eruptive rocks of the Ivrea belt, indiscriminately as metamorphosed sedimentary.?, The pietre verdi are now generally recognized to be in the main derived from eruptive rocks and some probably from tuffs or muds. At the same time the constant alternations, amounting to interstratification, of the 1 §. Franchi, ‘‘ Aleune metamorfosi di eufotidi e diabasi Alpi Occid.’’: Boll. R. Com. geol., 1895, p. 181 et seq. 2 Hence his well-known dictum: ‘‘In the Piémontese Alps plutonism is. a myth.”’ P.G. H. Boswell—Quantitative Methods in Stratigraphy. 168 pietre verdi with each other ; their stratiform, if not actually stratified, character in relation to the sedimentary rocks, and their frequent wedges and lenticular intercalations in the latter—all these phenomena on a large scale still present an intricate problem to which I shall refer in the descriptive sequel of the present paper.’ The problem . of the age of the pietre verdi in relation to the older rocks is, of course, rendered more difficult by the obliteration in the latter of organic remains through the ceaseless action of metamorphism past and present, or, in the words of Gastaldi: ‘‘ while Nature gives us on this Karth myriads of living species, she with relentless hand destroys all trace of former life elowne (To be concluded in our next number.) TV.—Tuer Apprication or PrerrotogicaL AND Quantirative Mrrnops TO SrraTIGRAPHY. By P. G. H. BOSWELL, A.R.C.Sc., D.I.C., F.G.S., Imperial College, London, S.W. (Concluded from March Number, p. 111.) LTHOUGH detrital mineral work is as yet initsinfancy, sufficient has been accomplished to show that we may look to it with success for indications of changes of drainage direction, evidences of denudation by reversal of the order of respective miner al assemblages from a sequence of rocks,? and generally for information regarding details of paleogeography. Professor A. de Lapparent referred to Professor L. Cayeux’s work as proving the proximity of land, com- posed of primary rocks, to Lille in Landénian times. Dr. H. H. Thomas was able to demonstrate the change in source, and therefore in direction of drainage, of the river-borne heavy minerals in the Bunter sandstones of South Devon,‘ the occurrence of garnets and staurolite being especially significant. Dr. T. O. Bosworth, in some preliminary work upon the detrital minerals of the Carboniferous Sandstone of the Midland Valley of Scotland, was led to the conclusion, partly by the respective presence and absence of garnets, that the beds could be divided into a series of great lenticular masses of sediment introduced from directions varying from north and north- west to north-east, east, and south.° Mr. W. R. Smellie has discussed in rather more detail the origin of the minerals in the Upper Red Barren Measures of the Glasgow Basin, the drainage having been _ from the west or north-west.® As a result of the study of the Tertiary sediments of Hast Anglia, the writer has been able to prove that the 1 Professor Bonney has described an instructive case of conversion of green- stone into schist on a small scale in the Bernina region, Q.J.G.S., 1894, p. 279 et seq. 2 This idea was suggested for contained boulders by Professor Charles Lapworth in connexion with the Carboniferous conglomerates of Halesowen in Worcestershire. 3 Traité de Géologie, 5th ed., vol. iii, p. 1492, 1906. 4 Q.5.G.S., vol. lviii, p. 620 (Sand of Bunter Pebble- bed), 1902; vol. Ixy, p. 229 (New Red Sandstone), 1909. ° Proc. Geol. Assoc., vol. xxiv, p. 57, 1913. § Trans. Geol. Soe. Glasgow, volt XIV, Pala Glel owe: 164 P.G.H. Boswell— Quantitative Methods in Stratigraphy. source of the Pliocene material was from the area of the Ardennes, etc., on the south-east, but that the minerals of the Kocene beds were derived from an entirely different direction, possibly from the west or south-west. The overlying Lower Glacial deposits were : derived, as their boulders also indicate, from the north, and possibly the north-east and north-west. These are broad generalizations only, but the subject is susceptible to more exact treatment which would lead to a correspondingly closer realization of ancient changes in geography. Unconformities are usually emphasized by the changes in mineral composition, and these support paleontological and field-evidence. Changes in the distribution of land and water and in the direction of the large rivers are thus revealed. As an outstanding example may be mentioned the contrast between the fine-grained residues, consisting largely of staurolite, kyanite, tourmaline, hornblende, and pyroxene, which are characteristic of the London Clay in Suffolk, and the coarse muscovite, red garnet, andalusite, staurolite, epidote, etc., of the overlying Boxstones at the base of the Crag of Rupelian, Miocene, or Diestian age. Recent work has possibly had a tendency to lead geologists to expect too much in certain directions from the comparative study of the residues of sediments, and it should therefore be stated at once that it is improbable that mineral constitution will have any cor- relative value over wide areas, certainly not comparable with that of fossils. From the nature of the subject we should expect various portions of basins of deposition to derive their material from different directions and sources. The writer has, however, endeavoured to show recently that mineral constitution, when fossils are rare or lacking (and if present, of wide range), has a distinct stratigraphical value over limited areas, when abundant samples are collected from numerous localities and horizons.t For this purpose the mineral assemblages of all the divisions of each of the geological stages of a district must be known. In connexion with these statements it should be said that the mineral assemblage of the Lower Greensand over most of its outcrop very closely resembles that of the Reading . Beds of South-East Suffolk and Northern Essex, which beds in turn are extremely similar in mineral composition to the Bagshot Beds of the area around Claygate and Oxshott in Surrey. Again, the mineral constitution of the various divisions of the Eocene beds in Kast and West Kent is much more similar throughout than in the corresponding divisions in East Anglia, where there is a greater variety of minerals. The respective Thanet Beds, Woolwich and Reading Beds, etc., in the two areas do not resemble each other in petrology, and no correlation could be attempted on such evidence alone. The composition of the Thanet Beds around Lille, as detailed by L. Cayeux,? is again different from either. ; Nevertheless, there are broad groupings which hold over a con- siderable area. Although the members of the Eocene Series differ among themselves, and each member may vary in composition over 1 Abstr. Proc. Geol. Soc., No. 973, p. 76, etc., 1915. 2 Ann. Soc. Géol. Nord, vol. xix, p. 264, 1891; also p. 90. P.G.H. Boswell—Quantitative Methods in Stratigraphy. 165 a wide area, all the Eocene beds in the London Basin appear to conform more or less to a general type characterized by the occurrence of abundant kyanite, staurolite, tourmaline, zircon, and rutile, and less commonly, green hornblende and small colourless garnets. The various beds of the Pliocene Series from Cornwall to East Anglia and Belgium all possess more or less similar mineral assemblages, the chief members of which are red garnet, muscovite, andalusite, staurolite, epidote, etc. The distinction from the Eocene Series is very marked. As a final example may be quoted the sands forming the lowest part of the Inferior Oolite, the mineral composition of which is very distinctive, and yet maintains practically the same character when the beds are traced from Yorkshire by way of Northampton, the Cotteswolds, Bath, and Yeovil to the Dorset coast. While correlation of smaller geological divisions over considerable areas is fraught with difficulty, the mineral constitution of the different beds is of great stratigraphical value, as has been stated, over limited areas. It has been shown, for example, that the Thanet Beds, Reading Beds, and London Clay in East Anglia have each a characteristic mineral assemblage by which they may be recognized, provided that we know also the mineral composition of all the other Tertiary beds from the top of the Chalk to the post-Glacial and Recent.! Speaking generally, each mineral assemblage remains constant over an area of nearly 500 square miles, and appears to be independent of the lithological variations of the bed containing it.’ That there is a limit to this constancy is shown by the fact that the Reading Beds, when traced as far to the south-west as Bishop’s Stortford and Hertford, begin to show a variation in mineral character. The change in mineral composition of the Reading Beds with respect to the underlying Thanet Beds may be due in part to difference of mechanical composition, and therefore to difference in conditions of deposition, resulting in concentration of certain minerals and decomposition of others, but whatever may be the cause the variation observed has an important stratigraphical value. The green and brown hornblende, pyroxene, biotite, apatite, etc., of the Thanet Beds disappear, and it is not until we reach the London Clay that some of these minerals reappear. The large and characteristic grains of kyanite, staurolite, and tourmaline present in the Reading Beds have disappeared in the London Clay, but green hornblende becomes _ abundant, and muscovite and colourless garnets more common. ‘The detrital material is of fine grain, and therefore provides the more contrast with the very coarse stuff found in the Boxstone Bed at the base of the Suffolk Crags. 1 Abstr. Proc. Geol. Soc., No. 973, p. 76, 1915. 2 Very recently (March, 1916), in a lecture before the Geologists’ Association, my friend and colleague, Mr. V. C. Illing, has claimed that the horizons of the unfossiliferous and oil-bearing sediments of the south-western part of Trinidad may be identified and correlated over a limited area by means of their mineral] assemblages. If this contention is supported by the evidence (and from an examination of the residues I believe it is), the hitherto purely academic study of » the petrology of sediments becomes at one bound of great economic importance. 166 P.G.H. Boswell—Quantitative Methods in Stratigraphy. The composition of the different zones of the Coralline, Red, and Norwich Crags is similar to, but not of so rich a type as, that of the Boxstones. The Chillesford Beds (late Pliocene) are much enriched in muscovite. The Westleton Beds (? early Pleistocene) show, as compared with the Pliocene beds below and the glacial deposits above, rather an impoverished assemblage which may have been derived from the Chalk and Kocene beds with a slight admixture of Crag detritus (garnets, etc.). The purity of the Westleton pebble- beds (mainly flint and quartz) and freedom from foreign boulders is interesting in this connexion. The glacial deposits yield, as no doubt would be expected when the variety and extent of the rocks laid under contribution are considered, a very rich mineral suite, the abundance and variety of which are unparalleled by any other deposit, and only approached by the Pliocene. Abundant garnets, amphiboles, and pyroxenes (sodic varieties included), epidote, micas, apatite, staurolite, kyanite, tourmaline, etc., make the deposits easily recognizable under the microscope or high-power hand-lens ( X 20). It is noteworthy that andalusite is not nearly so abundant as in the Crag or in the glacial deposits of the West of England. The post- glacial gravels, sands, and brickearths, and the river terrace sands, loams, and alluvium, contain similar mineral assemblages to the glacial beds, and are no doubt derived largely from them. The value and limitations of the application of petrographic methods to stratigraphy are well illustrated by the consideration of a sequence of deposits in one area such as that just mentioned. First we may consider the limitations (apart from those resulting from attempted wide correlation). The Upper and Lower Glacial beds of East Anglia differ much in field characters, in mechanical composition, and in their included boulders, indicating two different directions of advance for the ice which produced them. It is very difficult, however, to tell the Upper from the Lower beds by the heavy detrital mineral assemblage, notwithstanding the fact that their mechanical analyses conform to two very different types. This may be due to the mineral richness of each. Again, it was hoped that the various zones of the Red Crag, when traced northwards, might show, together with the increasingly boreal fauna, a corre- sponding change in mineral constitution (the basin was closed on the south and opened on the north in late Pliocene times). No such variation has been observed, and it seems probable that the drainage direction and rocks undergoing denudation to produce the Crag sands, etc., remained the same throughout Pliocene times. On the other hand, the advantages of the method are great. It has now become possible to identify any East Anglian bed (allowing for the limitations just detailed) from its detrital mineral suite, and to say when the mineral assemblage of any particular bed is pure, or when it has been contaminated with an admixture of material from another bed. A few actual examples may be quoted. Considerable glacial disturbance of the East Anglian deposits has frequently taken place locally in Southern Suffolk, etc., and it is often desirable to _ know whether a limited exposure shows a bed in situ, undisturbed and uncontaminated. Should the bed have been redeposited in P.G.H. Boswell—Quantitative Methods vn Stratigraphy. 167 Glacial times, even if its original characters are retained, its detrital minerals tell their tale. ‘The pale sands of the Reading Beds, Crag, and Glacial beds often resemble one another closely, and it has hitherto been difficult or impossible to identify with certainty an included mass of such sands in a large glacial disturbance.1 Hxami- nation of the mineral assemblage allows a determination to be made, for example, as to whether the sand is a pure Reading Sand or one contaminated by an admixture of glacial detritus. The pebble-bed at the base of the London Clay (on the horizon of the Blackheath Beds of the South of England) has in places in East Anglia been rearranged upon the shores of the Crag sea. This is indicated at times by the iridescent ferruginous coating upon the pebbles and the admixture of teeth and coprolites in the bed, but in some cases, except for the presence of reddish sand, it is difficult to say whether the bed is of Kocene or Crag age (that is, rearranged in Red Crag times). An analysis of the sandy material of the bed is sufficient to settle the point, for the Pliocene minerals are distinctive and easily recognizable, while those of the normal Kocene pebble-bed conform to the suite of the Reading Beds. In the area where overlap of the Thanet Beds by the Reading Beds takes place (in South-West Suffolk and North-West Essex), the latter assume the lithological characters of the former and rest directly on the Chalk. They contain a ‘bull-head’ flint-bed, and are glauconitic clayey sands. When isolated sections in Drift- covered outliers occur on the north-west of the main outcrop, it is sometimes 2 matter of difficulty, as, for example, at Kedington in the Stour Valley, to refer the bed observed to its proper place in the geological sequence. ‘The detrital minerals of the sands will usually be of service, and in the case quoted it was found that, while the Kedington deposit had the lithological characters, etc., of the Thanet Beds, its mineral composition showed it to be an outlier of Reading Beds, resting on the Chalk, but one which had been rearranged on the shore of the Crag sea. Cases might be multiplied, but the limited utility of the method must be apparent. At present it is premature to discuss the question of the stability of minerals in geological time. ‘The controversy upon the extent to which andalusite occurs in pre-Pliocene sediments in Western Europe is still fresh in our minds. The allied mineral, kyanite, appears to have a well-marked earlier limit in the English area, but how far the _ presence or absence is due to drainage direction is not certain. The extraordinary abundance of sharply crystalline apatite at a loamy horizon of the Thanet Beds near Ipswich, protected by a cover of Chalky Boulder-clay, is noteworthy as showing how an easily decomposable mineral may be preserved. The investigation of sediments ‘ hermetically sealed’ shortly after their formation, as, for example, gypsiferous deposits in the Permian and Trias, may by comparison yield interesting information as to the amount of decomposition which takes place in heavy minerals sub- sequently to their deposition. * The disturbance referred to may be 150 yards long and 40 feet deep. 168 P.G. H. Boswell—Quantitative Methods in Stratigraphy. Oscillatory and alternating current action has an effect, not only in eliminating the more easily decomposable minerals (e.g. some of the ferromagnesian minerals, apatite, andalusite, etc.), but also in concentrating the heavy detritus by a kind of natural jigging or panning. ‘ Pay-streaks’ may thus be produced. Parts of the pebble- bed under the London Clay in Suffolk exhibit an enrichment in zircon, rutile, ilmenite, and magnetite by this action, especially when there is evidence of current-action and contemporaneous erosion. The lenticles of grains of titaniferous hematite occurring in the basal Cambrian conglomerates of St. Non’s Bay, near St. David’s,! may have a similar origin. The richness of the Bagshot Beds in the heaviest minerals may be attributed to a like cause. As opposed to this concentration, we have the elimination of minerals (other than those which are more or less unstable) by conditions of deposit. The work of Thoulet and Retgers has shown that micas are absent from certain wind-formed deposits such as desert and dune sands, but examination of British blown-sand dunes has revealed their presence. Topaz tends to form flakes on account of its good basal cleavage, and may well float away; it has been suggested that andalusite may be lost in this way, by floating off during natural or artificial panning. The scarcity of apatite in many deposits is probably due to its disappearance by solution. It is more abundant in clays and loams than in sandstones where percolation is easy, but it does also occur in the latter. When the sediment has to be cleaned by long boiling with acid, much apatite undoubtedly dissolves, but, as in the case of the Boxstone Bed, some still remains. Professor C. G. Cullis and Professor W. G. Fearnsides have both suggested that the difference in solubility may be due to the presence of either or both chlor- or fluor-apatite, but usually the grains are so small, and the occurrence so uncommon, that micro-chemical proof is difficult. What may be called the intensive study of an area of sedimentary ‘rocks of various geological ages, surrounding an igneous or meta- morphic complex, is at present very necessary for the advancement of our work on the petrology of sediments. For this purpose we need to know exactly and in detail the mineral composition of neighbouring crystalline rocks, slicing alone not being sufficient. Crushing must be resorted to, and panning and separation with heavy liquids, in order that we may be certain of knowing all the accessory and rarer minerals and their relative abundance.? Following this, the study of the neighbouring sediments of varying geological age, considered stratigraphically, cannot fail to yield valuable data which will serve to indicate the extent to which the differences observed in assemblages of detrital minerals may be caused by direction of drainage, conditions of deposition, stability of minerals in geological time, and contemporaneous or subsequent sealing of minerals in sedimentary rocks. 1 'W. Jones, Proc. Geol. Assoc., vol. xxii, p. 232, 1911. 2 R. H. Rastall & W. H. Wilcockson, Proc. Geol. Soc., p. xxx, 1915. F. R. C. Reed—On the genus Trinucleus. 169 IVY. Concuusron. Detrital mineral assemblages are of considerable value for strati- graphical purposes over limited areas, but except for very broad divisions, as e.g. Hocene and Pliocene beds, cannot be used for wide correlations. Unlike fossils, minerals cannot show an evolutionary sequence or gradual variation, and there being comparatively so few species occurring in detrital sediments the number of combinations is very limited. Mineral suites, unlike life assemblages, therefore tend to recur. As in the case of minerals of igneous rocks, the relative abundance of the heavy components in sediments is of great determi- native value. Mere lists of detrital minerals occurring in sediments are therefore not sufficient; we need to know the size, colour, form, degree of alteration (if any), and other characters of each mineral, as well as its relative abundance. The zonal value of mechanical and mineral analyses has not yet been determined, partly because the rocks which yield the best heavy mineral crops, such as sandstones, loams, ete., do not lend themselves to zoning by fossils, while the clays and limestones, which often contain valuable life assemblages, contain frequently only a very small quantity of heavy minerals (other than authigenic). The connexion between the mechanical composition (e.g. of clays), as indicating differences in condition of deposit, and the contained faunas of various zones, has yet to be worked out, but the results may well be interesting. The goal to be sinned at is a Ienewiedies of the mineral and mechanical composition of every sedimentary rock in the British geological column, collection of material being made over as wide an area as possible. Cores of borings, as well as the records only, must be carefully preserved, and the beds met with subjected to similar analyses. The information obtained should be correlated with that yielded by the distribution of isopachytes and sub-surface ‘contours. V.—Sepewick Musrum Norss. NorEs on tHE GENUS ZrInucLEUS. Part IV. By F. R. COWPER REED, M.A., Sc.D., F.G.S. (Concluded from the March Number, p. 123.) MorpHoLocicaL CoRRELATIONS. EK have now finished the survey of the characters of the head- shield of Trinucleus sufficiently to enable us to discuss the vexed questions of the affinities, systematic position, and evolution of the genus; and from the foregoing details of the various species we can perceive that there are many difficult problems presented when we attempt to correlate its structure with that of other trilobites. Whether the peculiar characters of the genus are the result of degeneration or of the persistent retention of early phylogenetic stages or of a reversion to such stages is a matter of dispute. 170 F, R. C. Reed—On the genus Trinucleus. Lake,! in regarding the genus Orometopus as the earliest genus of the Trinucleide, concluded that it was not improbable that the ocelli in Zrinucleus represented normal compound eyes in a degenerate condition. Swinnerton? is also inclined to regard the absence of normal facial sutures and eyes not as a sign of early phylogenetic position but as secondary modifications of the Opisthoparian type of head-shield. For he does not consider the marginal suture as homologous with the facial sutures of the Opisthoparia and Proparia. These views are diametrically opposed to those put forward by Beecher,’ on which the classification of the trilobites has of late years been based. It may be pointed out that the present author, in 1898,* drew attention to the importance of adaptive changes in trilobites in connection with the loss of eyes and to the modifications of the head- shield which accompanied this loss, and it was maintained that blindness was not by itself any evidence of primitive phylogenetic position or of reversion to early stages of development. In the case of Zrinucleus blindness was considered to be an adaptation to special environment. Dollo® has treated this subject at considerable length, and has concluded that 7. concentricus lived in the mud under aphotic conditions as a member of the benthos. 1. Facial Sutures and Genal Areas. The controversy as to the presence or absence of facial sutures crossing the genal areas (apart from the marginal suture round the fringe) has been waged by many paleontologists.© But no satisfactory evidence of the occurrence of such sutures in young or adult has been produced, and McCoy’s’ figures and description of their presence in his genus Zretaspis are not supported by an examination of the specimens which he used. It is needless to recapitulate here the opinions of the various writers on the subject, for in the case of the English species here studied it has been possible for me to test the accuracy of their observations and conclusions. The line of ‘inquiry which they followed was not often comparative, and the principles of development were not understood by the earlier investigators. The researches of Beecher and other American workers have thrown a flood of light on the ontogeny and phylogeny of the trilobites, and from the adoption of the principles which they have established the position of Zrinucleus has been regarded as fairly secure amongst the most primitive group, Hypoparia. But recently, as above remarked, signs of dissatisfaction with this conclusion have been apparent. If we regard the genus as now possessing degenerate characters which it has acquired by the loss of certain structures, such as facial 1 Lake, Cambrian Trilobites (Paleont. Soc.), 1907, p. 45. 2 Swinnerton, GEOL. MaG., Dec. VI, Vol. II, p. 489, 1915. ° Beecher, Amer. Journ. Sci., ser. Iv, vol. iii, pp. 89-106, 181-207, 1897. 4 Reed, GEOL. MaG., Dec. IV, Vol. V, pp. 489-47, 552-9, 1898. > Dollo, Bull. Soc. Géol. Belgique, xxiii, p. 417, 1909. ® Woods, article on Trilobita in The Cambridge Natural History, vol. iv, Crustacea, pp. 226, 230-1, 244-5, 1909. * McCoy, Syn. Brit. Pal. Foss. Woodw. Mus., p. 146. F. R. C. Reed—On the genus Trinucleus. (il sutures and compound eyes, we should naturally turn to its earliest representatives for traces of these structures. It is in the first group, comprising Z. Murchison, T. Gibbsi, and 7. Htheridger, that the division of the genal areas by an oblique ridge is found, and this ridge has the course of the true facial suture in members of the Opisthoparia, and may possibly be regarded as marking the line of fusion between the free and fixed cheeks. The less modified stage in which fusion has not taken place would then be found in the genus Ampyz. In neither case are traces of compound eyes present along this line. The similar position of the pseudo-antennary pit in this genus and in Zrinucleus supports this comparison. Some species of Ampyz (e.g. A. nudus) also have oblique nervures originating from the same place in the axial furrows as in Zrinucleus, and running obliquely back across the cheek to the point of section of the posterior margin by the facial suture, which suggests that they are structures similar to the radiating nervures in Z. Murchisoni, and to the posterior or outer part of the ocular ridge beyond the ocellus in the 7. seticornis group. In the Conocoryphide (Eastman-Zittel, 1913), in which compound eyes and ocelli are absent, but in which narrow free cheeks are found separated off by true oblique facial sutures, there are groups of nervures radiating out from the same place on the axial furrows as in Zrinucleus. This diffuse innervation of the genal areas is a conspicuous feature amongst blind trilobites, and is especially developed in Liocephalus! of the Conocoryphide and in Dionide. The loss of eyes is found to be correlated with the straightening of the facial sutures and reduction in width and size of the free cheeks in higher genera (e.g. some species of J//enus* and Trimerocephalus)® ; or the facial sutures may entirely disappear by coalescence of the free and fixed cheeks, as in Typhloniscus* and some species of Phacops.° 2. Fringe. A difficulty meets us at this stage when we cease to regard the marginal suture on the edge of the fringe as representing the conjoint facial sutures as in Beecher’s theory, for the question of its correlation has to be faced. In answer to this we may suggest that it is possible that the lower plate of the fringe represents a reflexed anterior segment of the head-shield, and that the marginal suture is the divisional line between this and the first segment of the superior surface. The bending round ventrally of the anterior part of the crustacean head in its phylogenetic development is part of Bernard’s° annelidan theory of the origin of the Crustacea. Bernard held that — while the typical Crustacean head only consisted of five somites some of the trilobites possessed six somites in the cephalic shield. Early 1 Grénwall, Bornholms Paradoxideslag (Danmarks geol. Undersog., ii, No. 13), 1902, p. 102, t. 2, fig. 2. 2 Reed, Q.J.G.S., vol. lii, pp. 414-16, pl. xx, figs. 1-3, 1896. 3 Gurich, Verh. Kais. min. Ges. St. Petersb., ser. 11, Bd. xxxii, p. 359, +. xv, figs. 7a, b, 1896. 4 Reed, GEou. MaGa., Dec. V, Vol. V, p. 433, pl. xiv, figs. 1-3, 1908. > Gurich, op. cit., p. 362, t. xv, figs. 4a, b. © Bernard, Q.J.G.S., vol. 1, p. 411, 1894. 172 Ff. kh. C, Reed—On the genus Trinucleus. trilobites nearer the annelidan stock and with less fixed ordinal characters might have more segments bent round ventrally than higher forms, and the degree of coalescence of these inverted segments might vary. Thus, in the protaspis of Zrvarthrus there are two segments in front of the glabella which does not reach the anterior margin as it does in Sao; and ifthe immediate ancestors of 7rinucleus had such additional anterior somites one of them might have given rise to the ‘‘ lower plate”’, which, with its genal spines, would thus constitute an exceptionally modified and unfused segment. The condition of the adult head-shield of Zrinucleus would thus have | retained more primitive features than any other trilobite. We must admit that the ontogeny of 7. concentricus, so far as it is known, does not support this theory, but we must remember that the larval stages of the earliest species of Zrinucleus are unknown, and we have been led from previous considerations to regard Z. concentricus as one of the more specialized forms. In some other trilobites also the somite repre- sented by the free cheeks (the so-called ‘‘ ocular segment” of Walcott) might not be the first one in the composition of the cephalic shield. The rostral suture of Calymene and other genera on the above theory might be regarded as the abbreviated representative of the same suture as the marginal one in Zrinucleus, and the epistome as corresponding to the lower plate of the fringe. Walcott,’ by his study of the Mesonacide, has been led to consider it as not improbable that a seventh segment more anterior than the ‘ocular segment” (i.e. the segment comprising the free cheeks and carrying the compound eyes) existed in the primitive cephalon of the Mesonacide, and he sees traces of it in the larval structure of Olenellus Gulbertt and in the cephalon of Olenelloides and Callavia bicensis; so that in tabulating the somites included in the cephalon he gives first the ‘‘ anterior border segment’, secondly the ‘‘ ocular segment”’, and thirdly the first glabellar segment from which the ocular ridge and palpebral lobe are developed. It may here be mentioned that though the genal spines belong to the ‘‘ocular segment’ in the Opisthoparia, yet in the Proparia they belong to one of the posterior segments and perhaps to the fourth glabellar segment of the Mesonacide, which in some genera (e.g. Olenelloides) is produced at its lateral termination to form the so-called intergenal spines on the posterior border. The genal spines of the Proparia are therefore not homologous structures with those of the Opisthoparia, a point of importance rarely recognized ; and it would therefore not be wholly contrary to expectation to find the genal spines of the genus Zrinucleus belonging to a different somite of the cephalon, and possibly to the first or ‘‘ anterior border” one of Walcott, bent under ventrally. Whatever value may be attached to the above theoretical con- siderations, it must be admitted that there is a possible interpretation on these lines, though it would upset our whole accepted ideas of the morphological correlation of the parts of the head-shield. Another suggestion which may be offered to explain the mar reinal suture is that it is connected with the process of ecdysis; for Limulus 1 Walcott, Smithsonian Mise. Coll., vol. liii, No. 6, p. 238, 1910. ! | \ ‘ F. R. C. Reed—On the genus Trinucleus. 173 and Apus are said to moult by splitting along the frontal edge of the . carapace. This would then have to be regarded as a special adaptation, and perhaps of no phylogenetic importance. The facial sutures in trilobites are usually considered to have been of some use in ecdysis, and compensation for their loss in Zrinucleus may have been obtained by this means. The fringe would according to this hypothesis be merely brought about by the flattening and broadening of the ordinary cephalic border, while the perforations through its substance might be derived from the multiplication of pits similar to those seen in the marginal furrow of Dionide,’ Harpes, and Euloma.* The lower plate of the fringe would represent the doublure or reflexed portion of the border. The complete fusion of the pits of the upper and lower surfaces of the fringe would be secondary. 3. Ocular Ridges and Nervures. The history and relations of the ‘‘ ocular ridge” or ‘‘eye-line’”’ in Trinucleus now demand attention. It is generally looked upon as a primitive character. Walcott (op. cit.) has shown how it forms part of the third cephalic (i.e. first glabellar) segment in the case of the Mesonacide; and in Cambrian trilobites belonging to the - Opisthoparia as well as to the Harpedide this structure is well . developed, while, as is well known, it persists in some later genera. It is usually accepted without question that the similarly named structure in Zrinucleus is homologous with this ‘‘eye-line”’ of the Olenide, ete., though in the latter its point of origin does not appear to be so constant, for it frequently arises close to the anterior end of the glabella instead of strictly opposite the first glabellar furrow. It also runs out to compound eyes, not to ocelli, and the eyes are situated on the facial sutures. It is remarkable that in the earliest representatives of the genus Zrimucleus (Group 1) the typical ocular ridge does not occur; but it is found in the larval stages of Z. con- centricus, and is well developed in the adult of 7. setecornis of our second group. Till we know the ontogeny of 7. Murchisoni or its allies we cannot come to the conclusion that the irregular radiating bunch of nervures is more primitive than the definite ocular ridge or optic nerve, at any rate in this genus. But the stratigraphical succession of species points this way, if we dismiss the idea of degeneration. In most of the Conocoryphide® (e.g. C. Sulzert, Schloth., and Erinnys venulosa, Salt.) there is one of the nervures more strongly developed than the rest, and it forms the trunk from which they branch; its position corresponds with that of the eye-line of the Olenide. If we regard the ocelli of Zrinucleus of Group 2 to be the degenerate successors of the compound eyes of other trilobites and believe that the facial sutures have been obliterated by the complete fusion of the free and fixed cheeks, there is no difficulty in accepting the view supported by Lake and Swinnerton (op. cit.) that the ocular ' Reed, GEOL. MaG., Dec. V, Vol. IX, p. 200, Pl. XI, Figs. 3-6, 1912. * Brégger, Die Silur. Htagen 2 und 3 (1882), p. 98; Reed, GEOL. MaG., Dec. IV, Vol. VII (1900), pp. 251, 255. ® Grénwall, Bornholms Paradoxideslag, pp. 82-104, 1902. 174 F. R. C. Reed—On the genus Trinucleus. ridges in Zrinucleus are homologous with those in other genera, such as members of the Olenide. But if we maintain that the marginal suture represents the facial sutures, great difficulties seem to be introduced. For the relics or rudiments of the compound eyes, according to Beecher’s theory, would then have to be sought at the edge or below the edge of the fringe, and the ocular ridges as they now exist must have been shortened considerably. The ocelli then would not be placed at the original terminations of these ‘‘ eye-lines”’ but somewhere along their course, and could not be homologous in position or origin with the compound eyes. The larval characters of T. concentricus, which has the ocular ridge and tubercle developed, do not lend any support to the view that the ocular ridges have been reduced in length and are shrunken remnants of longer ridges. Thus we see another line of evidence tending to contradict Beecher’s theory. 4, Eyes. The absence of eyes in genera of the higher families is found to be accompanied by modifications in the head-shield on the same lines (apart from the development of a fringe), and no genetic deductions can be drawn from this want of visual organs. In the Illenide, Phacopide, and Cheiruride we find instances of their absence. On the other hand, the presence of compound eyes is not invariably associated with the retention of facial sutures, as we find in the case of certain species of Acidaspis, in which the sutures have been obliterated or lost by the coalescence of the free and fixed cheeks. The extension of the ocular ridge to the postero-lateral angle of the genal area may find its explanation in the continuation of the same structure on the ‘‘ocular segment’? in larval forms and some adults of the Mesonacide, and if this is a correct view it would mark the original course of the posterior branch of the facialsuture. There is, however, another explanation possible by which we could regard it as merely the,result of the concentration of those nervures which we found in some of the early species of Zrinucleus convergently trending to this angle. The enlargement of one nerve at the expense of the others in this outer portion of the genal area may have taken place contemporaneously with the development of the ocular ridge from the axial furrow to the ocellus. And in support of this view we find traces of a similar strong nervure in Ampyx nudus, which has a facial suture placed much further out and independent of it. It may be here mentioned that no lenses have yet been detected in the so-called ocelli of any species of Zirinucleus, though they are well developed in Harpes and are schizochroal. The visual function of these genal tubercles in Zrinucleus is generally assumed, but it may be that they had some other sensory function, or that their visual powers (if they are regarded as degenerate compound eyes) have become obsolete. The tubercle on the pseudo-frontal lobe of the glabella, which is generally present in Zrinucleus, and has precisely the same appearance as those on the cheeks, may be representative of the ‘dorsal organ”’ of the Phyllopods, which is supposed to be excretory rather than sensory in its function. But it may represent a median unpaired ocellus, and it is frequently present in species which have si Ee F. R. C. Reed—On the genus Trinucleus. ATS no genal tubercles, though in some cases it appears to be completely absent. 5. Specialization. It is not only in the head-shield of Zrinucleus that we can observe extraordinary specialization and the modification or loss of phylo- genetically primitive characters. For the small and constant number of the thoracic segments, and the uniform type of pygidium as well as its relatively large size and its composition of many fused segments, indicate a considerable divergence from and advance beyond the condition of the many-ringed thorax and small pygidium of the Conocoryphide and Olenide or even the Harpedide, in spite of the latter having often been regarded as closely allied to Zrinucleus. It does not seem that Zrinucleus is in the direct line of any of the other groups of trilobites, but was an early offshoot of the Opistho- paria, to which it is linked (though not by direct phylogenetic connection) by Orometopus and especially Ampyx. Its nearest homcomorphs are Dionide and Harpes, but the latter retains more of the primitive trilobite characters (e.g. many segments to the thorax and a small pygidium), and does not show such extreme specialization except in the head-shield. Instead, therefore, of placing Zrinucleus as one of the simple lowly types of trilobites illustrating an early stage in the history of the class, it seems more probable that we should regard it as a modified and degenerate form belonging to the Opisthoparia which has been specialized and adapted to a peculiar environment. Summing up the results of our study of the head-shield of Zrinucleus and balancing the probabilities of the various theories in connection with its structure and origin, we seem led to conclude that the ancestors of this genus branched off from an Opisthoparian stock and suffered degeneration of certain parts in combination with extreme specialization of other parts to fit them for a peculiar environment. Under the aphotic condition of the benthos burrowing in the mud rendered compound eyes unnecessary and they therefore degenerated, while in compensation for the loss of these organs a complete system of nervures developed over the glabella and cheeks. The fixed and free cheeks fused along the line of the facial sutures and ultimately became completely obliterated. The border of the head- shield broadened out and was folded in ventrally so as toform a lower plate, while to facilitate moulting a line of fission was formed along its edge. Perforation of both layers of this border took place on an extensive scale, and the corresponding pits of the two layers frequently communicated. A change of habits in some of the species led to the development of ocelli by rudiments of the compound eyes persisting from larval to adult life, but in other cases this renewal of visual organs was found of no value, and therefore again lost. In conjunction with the presence of the ocelli the optic nerve (ocular ridge) was strengthened and redefined. These changes, which suggest the retention till maturity of larval features or the re-acquisition of organs of which the rudiments had only been left, do not appear to have been strictly successional, but to have been _ developed as occasion required. 176 Reviews—Prof. Joly’s Radio-activity and Geology. P.S.—Since the above was written Professor Swinnerton’s concluding paper on the classification of the Trilobites has been issued(Gnot. Mae., Dec. VI, Vol. II, p. 543, December, 1915). In it the three families Trinucleide, Raphiophoride, and Harpedide are placed in a separate ' sub-order with three other families as a provisional appendix, and their line of descent is traced back to a Conocoryphid-lke stock. This view is in general accordance with my conclusion that Zrimucleus is more probably connected with the Opisthoparia than with the ill-established group Hypoparia. RAVLEWwSs- ———<———— I.— Rapio-acrivity AND GEOLOGY. Tar Braru-time oF THE Wor LD, AND oTHER ScrenTiFic Hssays. By J. Jory, M.A., Sc.D., F.R.S. pp. 307. T. Fisher Unwin. 1915. 10s. 6d. net. ({VHIS volume is an eloquent witness to the love which its versatile author feels for all the activities of nature. It contains twelve essays, mostly written during the last few years, dealing not only with geological problems but also with such diverse subjects as the abundance of life, the colours of flowers, the ‘canals’ of Mars, the photographic image, the application of radium to medicine, and the physics of skating. These last are mentioned only to show the far-flung interests of Professor Joly and the broad appeal of his book; for it will be convenient to restrict the discussion in this place to those of the essays which are specifically geological: The Birth-time of the World, Denudation, Mountain Genesis, Alpine Structure, and Pleochroic Haloes. The problems considered fall approximately into two categories. First, the measurement of eeological time by denudational and radio-active processes, and second, the genesis of mountains. Pleochroic haloes, their explanation, and their application to determining the age of the minerals in which they occur, form the subject of a delightful essay which is already so well known that it calls for no comment here, but one of admiration. Some of the results obtained by Professor Joly for the age of the earth, based on geological methods, are as follows :— 1. From the thickness of sediments . : 100-134 million years. oe a5 mass of sediments : : 87 i 75 3. ua sodium in the ocean . : 99-105 ‘is +4 It is unfortunate that the data used in arriving at an estimate of the detritus borne by the rivers to the sea do not include the recent results for the whole of the United States (Dole & Stabler, Water Sup. Pap., U.S.G.S., No. 284, 1910). Inthe light of this work the figure given for the annual increment of sediment—10,700 million tonnes, + 11 per cent for bottom load—seems to be much too high. Here it may be mentioned that Professor Joly uses the term ‘‘ sedimentary rock’? where mechanically transported detritus is meant, as, for example, when he states that ‘‘ 100 tons of igneous rock yields rather Reviews—Prof. Joly’s Radio-activity and Geology. 177 less than 70 tons of sedimentary rock” (p. 48). Actually, of course, more than 100 tons of sedimentary rock are produced, because most of the materials carried in solution to the ocean are afterwards incorporated by sediments, and, moreover, a good deal of material is abstracted from the atmosphere during the process of weathering. However, since the same meaning is consistently assigned to ‘‘sedimentary rocks” throughout the calculations, no error is thus introduced in the time estimates. The amount of sodium annually contributed to the ocean is given as 175 million tons. This figure implies that the sediments now undergoing solvent denudation must lose all the sodium they contain, for the average amount of sodium in sediments, as exposed on the lands, is only 0°85 per cent. Unless, indeed, the igneous and other crystalline rocks of the earth’s surface—and these do not cover more than a quarter of the land areas—also lose all their sodium (and we know they do not), then the sediments must lose more than they appear to have originally contained. ‘This remarkable discrepancy shows either that the statistics of denudation are wrong, or that solvent denudation is now far more active than it has been on an average in the past, or that sodium is in some way restored to the sediments from sea-water. The latter possibility, exemplified by wind-borne salt, is further suggested as probable by the presence of salt waters in deep mines, and by phenomena of adsorption, whereby oceanic salts would become concentrated and trapped in sediments while they yet lay on the sea-floor. That denudation may be unusually active at the present time is a view that Professor Joly does not support. In favour of his contention to the contrary, he quotes figures to show that Europe, with the lowest average elevation among the continents, is undergoing the most rapid denudation. However, it is just in Europe that agricultural pursuits have been longest followed, and who can doubt that agricultural processes may enormously add to the ease with which the natural agents of denudation can attack the land. In ‘the case of the other continents there does appear to be a relation between mean elevation and total denudation. In so far, therefore, as the continents and mountain ranges stand higher to-day than they have averaged in the past, we may expect the intensity of denudation to be correspondingly increased. The remaining possibility, that the statistics of denudation are wrong, only enhances the difficulty, for when the United States data are _ added to those already available, the amount of detritus is found to be less than Joly gives, while the amount of sodium remains practically the same. It is possible, however, that owing to the difficulty of estimating sodium in river waters, errors may arise from inaccuracies of analysis. If the geological methods of measuring time as interpreted by Professor Joly are reliable, then it is necessary to show in what way the radio-active estimates are wrong. The latter give for the earliest known igneous rocks an age of about 1,500 million years. The pleochroic halo method gives a most probable value of 400 million years for the Leinster Granite (late Silurian or early Devonian). DECADE VI.—VOL. III.—NO. Iy. 12 178 Reviews—Field Analysis of Minerals. Professor Joly throws out the suggestion that the rate of transformation of uranium may have been in the past more rapid than now. This, of course, if it could in any way be demonstrated, would necessitate a reduction of the time estimates based on such transformation. The suggestion can, however, be tested in another way, for if the rate of transformation were formerly more rapid than now, then the amount of energy liberated during any given period of the past would also be creater than now. That is to say, if the earth has cooled from a high temperature such as 1,000° C. at or near the surface, the radiothermal energy must have retarded the rate of cooling in the past more tham it does now. Under these circumstances, if the earth were able to cool at all, it would certainly cool so slowly that its age would be much higher than the 1,500 million years required by the accumulation of lead. Joly’s suggestion, then, is incompatible with belief in an earth originally molten at or near the surface. Since no basement. has ever yet been found at the bottom of the geological succession that has not been molten at some time or other, the period required for cooling down to present conditions must have been even greater than that demanded by uninterrupted cooling from a molten state. Thus, the assumption that radio-active transformations have not been uniform leads to far more serious difficulties than does the alternative view that geological processes have not been uniform. In his essays on mountain genesis and structure, Professor Joly introduces a less controversial subject. He shows that the accumulation of sediments leads not only to thermal blanketing of the rocks beneath, but also to an additional rise of temperature due to the emission of heat from the radio-elements contained in those sediments. In this way, thick lens of sediments and the rocks below them become so weakened by the rising temperature that when the earth contracts they are folded and upheaved by compression, in preference to cooler and more rigid portions of the crust. The process is worked out im convincing detail, and there canbe no doubt that Professor Joly has added to the theory of mountain-building a most significant contribution. Before closing this review, which by no means covers the whole scope of the book, the writer feels that he should express the pleasure that he has experienced in reading so admirable a collection of essays. The rhythm of life, the majesty of the mountains, the inner secrets of the rocks, and the stimulating companionship of nature—all are revealed in its pages, and reflected in the beautiful photographs with which they are illustrated. Anceue Eee IJ.—Fierp Awnatysis or Minerats. By G. D. McGricor. The Mining Magazine, pp. 86. 1915. 3s. 6d. net. fV\HIS book has been written professedly to meet the requirements of the traveller.and prospector, and in keeping with that purpose it has been published in a size convenient for the pocket. The advantages of a small strongly bound book in the field may readily be granted, but when the author, in his ‘‘ Prefatory Remarks and Advice’’, recommends the traveller also to take with him Brush Reviews—Determinative Mineralogy. 179 and Penfield’s bulky Manual and Rutley’s Elements of Mineralogy, one wonders why the smaller book should have been compiled at all. Certainly it only claims to deal with analysis, but analysis alone is generally a cumbersome and sometimes an insufficient means of determining minerals. Asa supplement to the many excellent books on determinative mineralogy which already deal with blowpipe analysis (such, for example, as those noticed below) this little handbook can claim at best only a very limited field. Unnecessary space is devoted to wet methods of analysis, and this might have been better occupied by lists of minerals with their composition and simpler properties. Microcosmic salt is said to be commonly termed ‘micro’; sodium carbonate is referred to as ‘soda’; the use of the scale of hardness is mentioned, though the scale itself is not given. IJ1.—Dererminative Mrneratocy. ByJ.V. Lewis. Wiley & Sons. 2nd ed., revised. pp. 155. 1915. Price 6s. 6d. net. ‘P\HIS edition differs from the first in no essential particulars, but. it is improved by the addition of several new features that greatly enhance its usefulness. A number of delicate tests have been introduced for various elements or minerals, and the determinative tables have been made more complete. The only blemish that disfigures the pages of the book consists in the use of a large number of abbreviations, many of which are not only ugly but, if saving of space was the ideal sought after, quite unnecessary. The index is good, and the references to any mineral can be located with ease. IV.—Etements or Mineratoey. By Franx Rouriey; revised by H. H. Reap ; introduction by G. T. Hottoway. Murby & Co. 19thed. pp. 394. 1916. Price 3s. 6d. net. UTLEY’S well-known book has long been a favourite; among students for its cheapness, among teachers for its thoroughness ‘and general accuracy, and among prospectors for its completeness and convenient size. If this was true of the old ‘ Rutley’, then the present revised and largely rewritten edition ought to enjoy a still higher degree of popularity. Not only is the work brought com- pletely up to date, but the presentation of the facts and the aspect of each printed page is much more attractive than formerly. The inclusion of a chapter on optical properties and its application to the determination of the silicate minerals will be much appreciated. The economic side of mineralogy is given considerable prominence, and attention is directed to the mode of occurrence and uses of minerals rather than to localities alone. The arrangement of minerals according to their most noteworthy element has many advantages, especially from the point of view of determination and economics. In each case an introduction to the element in question is provided, including a list of the chief minerals into which it enters. The book concludes with a useful glossary, a table of the geological systems, and a very complete index. MReviser and publisher are alike to be congratulated on their success in building on the sound foundation of Rutley a most valuable and comprehensive work. 180 Reviews—The E'pigene Profiles of the Desert. V.—Tue Epiczne Prorites or tar Desert. By A. C. Lawson. University of California Publications, Bull. Dept. Geol., vol. ix, No. 3, pp. 28-48, 1915. (| \HE author discusses the effects of arid erosion on an uplifted land mass, and explains the origin of the three elements that enter into the profile thus evolved—rock slopes having an angle of less than 35°, alluvial fans with slopes rarely exceeding 5°, and wide- spread plains. The area to which the paper chiefly refers is that of the Great Basin, in which wind scour is held to be ‘‘an extremely inefficient agent in the evolution of the . . . relief’’. The encroach- ment of alluvial embankments on the rocky slopes is attributed to mechanical disintegration, while scanty rains and occasional cloud- bursts sweep the detritus to lower levels. Ultimately the cycle ‘culminates in the ‘panfan’—a vast alluvial surface of aggradation below which all rock slopes have at last been buried. As corrasion and deflation are dismissed as unimportant, the paper must be regarded as applying to a particular desert rather than to deserts in general. VI.—Brisr Noriczs. 1. Trrasstc Rocks or Wirrat.—Messrs. Greenwood & Travis have given us part ii of their paper on the Mineralogical and Chemical Constitution of the Triassic Rocks of Wirral. The paper appears, like part i, in the Proc. Liverpool Geol. Soc. (xii (2), 161-88, 1915), and deals with the chemical side. The authors arrive at the general conclusions (1) that the material of the Wirral Trias, as a whole, was derived from igneous rocks of a granitoid nature; (2) that the Bunter and Keuper differ in the physical conditions of the grains, but agree in containing the same minerals; (3) that the Keuper was probably derived direct from the disintegration products of an igneous mass; and (4) that the Bunter had ‘previously formed part “of an earlier arenaceous rock-mass. 2. A New Mernop in Zoockocrarpay.—The study of geographical distribution is so intimately bound up with paleeogeography, and there- fore with geology, that we make no apology for directing the attention of our readers to an important paper by Mr. R. J. Tillyard, M.A., of Hornsby, N.S.W., ‘‘On the Study of Zoogeographical Regions by means of Specific Contours’’ (Proc. Linn. Soc. N.S. Wales, vol. xxxix, pp. 21-48, pl. i, 1914). Taking a well-defined group, Mr. Tillyard - plots down the number of species recorded from all known localities, and calls the lines bounding tracts with the same number ‘‘ specific contours’’. He illustrates his method by applying it to the dragon- flies of Australia, with interesting results. Another paper by Mr. Tillyard is a ‘‘ Study of the Odonata of Tasmania in relation to the Bassian Isthmus’’, that portion of land which once (but when ?) connected Tasmania with the Australian mainland (op. cit., vol. xxxvill, pp. 765-78). 3. Tae Form anv Consritution or tHe Earta.—An interesting paper by L. B. Stewart delivered as the Presidential Address to the i i ln ll a nee Brief Notices. 181 Royal Astronomical Society of Canada in 1914 (reprinted Smithsonian Rep. for 1914 (1915), pp. 161-74) summarizes recent geodetic work on the form and constitution of the earth. The paper consists mainly of an account of the gradual measurement of the size of the earth, and finally discusses isostasy and allied problems. He accepts isostasy, and adopts the view that the earth is a cooling and shrinking body of which the crust accordingly is under the continual necessity of adapting itself to smaller space; and to this contraction he attributes earthquakes, and as probably none of them originate at a greater depth, he concludes the material at greater depths behaves as a fluid. He also holds the view that the earth as a whole is more rigid than steel. He summarizes the conclusions as to the rate of earthquake waves at different depths. 4. Swattow-warer Depostrion 1n THE CAMBRIAN OF THE CANADIAN CorpituEra.—Under this title Mr. L. D. Burling publishes in the Ottowa Naturalist for November, 1915, evidence of shallow-water conditions during the deposition of Cambrian limestones in British Columbia and Alberta. Such evidences are mud-cracks, ripple-marks, and interformational conglomerate. Such proofs occur in the Middle Cambrian Mount Stephen formation, though not, of course, in the Burgess Shales; also at the base of the Upper Cambrian, in the Bosworth formation, where also are large casts of salt crystals. 5. Tue Favunistic Inrivence oF LitrwoLocicaL CHARACTER.— Mr. L. D. Burling (Bull. Geol. Soc. America, vol. xxv, p. 421) has studied the relation of the genera and species of Brachiopoda to the sediments in which they are found, so far as concerns the Cambrian _.and Lower Ordovician rocks mainly in North America. Dividing sediments into shale, sandstone, and limestone, he finds that 41 per cent of the genera and sub-genera, 74 per cent of the species and varieties, appear to have been identified from but one type of sediment. About half of these, however, are represented by single species in single faunules or localities. Although the nature of the sea-floor does thus appear to exert some influence on the nature and number of the species (there are fewest in shale, most in limestone), still most species can accommodate themselves to changes in the character of the sediment, especially when the change is from more to less elastic. The study is of enough importance to be extended to other groups of animals. 6. Grozocists’ Association or Lonpon.—Mr. George W. Young ended his presidency of this body on February 4, when he read his second annual address ‘‘On the Geological History of Flying”’. This year he dealt with Invertebrates, last year with Vertebrates. Mr. George Barrowe (late of H.M. Geological Survey) succeeded to the presidential chair. The usual list of proposed excursions is issued, many close to London and of exceptional interest. The ‘long excursions’ have not yet been, fixed. 7. Tue Zootoercat Recorp.—The annual volume for 1914 (vol. 11) has just appeared. Paleontologists may be reminded that all fossil forms are included, and that the literature of each group is published separately at a small cost. At the present moment the Zoological 182 Reports & Proceedings—Geological Society of London. Record is the only list available for 1914. That for 1915 is in preparation, and a list of the parts can be obtained from the Secretary of the Zoological Society. 8.—Opsrp1aN FRomM Hrarnrinnugryeeur, Icetanp: rs Lirnopaysz anp Surface Marxines. By F. E. Wricur. Bull. Geol. Soc. -Am., vol. xxvi, pp. 255-86, 1915. N his work on the Obsidian Cliff spherulites, Iddings came to the conclusion that the expansion of liberated gases played little part in the development of lithophyse. The examples studied by Dr. Wright indicate, on the contrary, that the volatile components liberated with the radial crystallization of the spherulites ‘‘ aided materially in the original formation and subsequent enlargement of the lithophysal cavities’. Other structures are also discussed, notably surface pits and grooves etched by hot circulating solutions, which bear a striking resemblance to the surface markings of moldavites. While the terrestrial origin of the latter is not proved, it is shown that their external form and internal strains afford no evidence of an extra-terrestrial origin. REPORTS AND PROCHHDINGS- I.—Grotoeicat Socrrty oF Lonpon. ANNUAL GENERAL MEETING. February 18, 1916.—Dr. A. Smith Woodward, F.R.S., President, in the Chair. The Reports of the Council and the Library Committee, proofs of which had been previously distributed to the Fellows, were read. It was stated that of the 31 Fellows elected in 1915 (6 less than in 1914), 23 paid their Admission Fees before the end of that year, making, with 8 previously elected Fellows, a total accession of 31 in the course of 1915. During the same period, the losses by death, resignation, and removal amounted to 90 (34 more than in 1914), the actual decrease in the number of Fellows being, therefore 59 (as compared with a decrease of 11 in 1914). The total number of Fellows on December 31, 1915, was 1,250. The Balance-sheet for that year showed receipts to the amount of £2,836 2s. 10d. (excluding the balance of £105 18s. 5d. brought forward from 1914), and an expenditure of £2,306 7s. 11d. Reference was made to the fact that three out of the four members of the staff of permanent officers were still engaged in various duties under the War Office, and that temporary assistants had consequently been appointed. ‘The decease of the former Assistant Librarian, Mr. William Rupert | Jones,! was announced, and the awards of the various Medals and Proceeds of Donation Funds? in the gifts of the Council were enumerated. 1 See Obituary, GroL. MaG., February, 1916, p. 96. 2 See brief report, GEOL. MaG., March, 1916, p. 135. Reports & Proceedings—Geological Society of London. 183 The Report having been received, the President handed the Wollaston Medal, awarded to Dr. Alexander Petrovich Karpinsky, to M. Constantin Nabokoff, Councillor of the Imperial Russian Embassy, addressing him as follows :— Councillor NABOKOFF,—The Council of the Geological, Society has this year awarded the Wollaston Medal, its highest distinction, to Dr. Alexander P. Karpinsky, Honorary Director of the Geological Committee of Petrograd, which is responsible for the geological survey of the Russian Empire. Dr. Karpinsky’s activities have extended over a period of more than forty years, and so long ago as 1874 he made one of his most important discoveries, that of a marine formation in the Ural Mountains intermediate between the Carboniferous and the Permian Systems. This Artinskian Stage, as Dr. Karpinsky termed it, has now been traced in Russia almost from the Arctic Ocean to the Caspian Sea, besides being recognized in more remote regions, as in the Salt Range of India. Its interesting fauna has also been the subject of several important monographs, of which one of the most valuable is that on the Ammonoids, contributed by Dr. Karpinsky himself to the Imperial Academy of Sciences of Petrograd in 1889. Dr. Karpinsky has continued to take the deepest interest in the geological problems presented by the Urals, and has treated them with remarkable versatility from every point of view, whether tectonic, petrographical, or paleontological ; but as official director of the surveys from 1885 to 1903 he also extended his researches to many other districts, and took a prominent part in the preparation of the beautiful geological maps which were issued during his period of active service. The useful Geological Map of Russia in Europe, which he edited in 1893, is especially well known. All Dr.-Karpinsky’s work is characterized by the most painstaking thoroughness, of which I need only cite his two exhaustive memoirs on the Carboniferous ichthyolite, Helicoprion, as conspicuous examples. Those who have the privilege of his personal acquaintance recognize in him an unassuming and enthusiastic student, still absorbed in following and aiding the progress of our science, and pre-eminently one whom the Geological Society delights to honour. } The Council will be glad if you will convey this medal to Dr. Karpinsky as a token of its esteem and admiration, with an expression of its best wishes. Councillor Nabokoff replied in the following words :— Please accept my sincere thanks for the honour that you have done me in asking - me to come here to-day and to convey to Dr. Karpinsky, with the expression of your good wishes, the Wollaston Medal which the Council of the Geological Society has awarded to him. I feel certain that this great distinction will be deeply appreciated by the recipient of the medal, as well as by the Russian Geological Committee as a high tribute to their Director. My distinguished friend, Dr. H. H. Hayden, Director of the Geological Survey of India, who crossed the Pamirs from India into Russian Turkestan a few months before the War, has often expressed to me the wish and hope that the highly interesting and valuable scientific researches which have been carried out on both sides of the Pamirs by the British and Russian geologists may be linked up and conducted on a basis of firmer and more complete unity and co-ordination. I venture to avail myself of this opportunity of expressing on behalf of my countrymen the same wish, and the confident hope that the ties of friendship which now unite Britain and Russia may extend from the fields of battle to the lofty peaks of science and enlightenment. The President then handed the Murchison Medal, awarded to Dr. Robert Kidston, F.R.S., to Dr. Finlay Lorimer Kitchin, M.A., for transmission to the recipient, and addressed him as follows :— Dr. KITcHIN,—The Council has awarded to Dr. Robert Kidston the Murchison Medal as a mark of its appreciation of his numerous and valuable contributions to our knowledge of fossil plants, especially those of the Carboniferous Period. For nearly forty years he has devoted himself to an exhaustive and successful 184 Reports & Proceedings—Geological Society of London. study of the external characters of the plant-remains associated with the various coal-seams ; and in this manner he has acquired an unrivalled knowledge of the distribution of the Carboniferous flora, which has proved of fundamental importance both to the geologist and to the practical miner. I may mention, as examples of this work, his classic memoirs on the fossil plants of the Yorkshire and Staffordshire Coalfields and of Belgian Hainaut. During more recent years he has also extended his researches to various facts of structure and morphology which have a direct bearing on evolutionary problems. His memoir on the fructification of Newropteris heterophylla was the first description of the seed of a Pteridosperm in direct continuity with the frond ; while his account of the microsporangia of the Pteridosperms first demonstrated the nature of the male organs in plants of this transitional group. His description of the internal structure of Szgillaria, and his remarkable series of memoirs, with the late Professor Gwynne- Vaughan, on the evolution of the Osmundacexz, must also be specially mentioned. While pursuing his researches he has continually recognized the importance of careful field-work, and has thus made a large and valuable collection of specimens, which has always been placed freely at the disposal of his fellow- paleobotanists. In transmitting this medal, please express our hope that he will treasure it not only as a token of our admiration but also of our gratitude. Dr. Kitchin replied in the following words :— Mr. President,—It is gratifying to be the transmitter of the Murchison Medal to one who, a Scotsman himself, has laboured so long and so assiduously in elucidating the stratigraphical bearings of the Carboniferous flora. Dr. Kidston, I feel sure, would have received this medal with enhanced pleasure, could he have listened to your graceful and appreciative references to his work. He asks me to express to you his great regret that he is unable to be here in person ; and I may add that he is detained by responsible public duties, which have the first claim upon his time. Dr. Kidston writes: ‘* Will you please express to the President my sorrow at not being able to be present to thank the Society personally for the honour that they have done me in presenting me with the Murchison Medal, an honour which, it is needless for me to say, I very much value and appreciate. ‘‘The award of this medal brings vividly to my memory that a number of years ago the Society awarded to me the Balance of the Proceeds of the Murchison Geological Fund, and I would like them to know that these proceeds were spent in the purchase of books dealing with Paleozoic Botany. It is only workers situated where not a single book on their special subject of study is obtainable for reference who can fully appreciate the value of the help that _I received from that award, and I hope that the books will eventually be placed where they will be of help to others. ‘* T have now only to thank the Council of the Geological Society once more for its kind and encouraging recognition of my work.’’ In presenting the Lyell Medal to Dr. Charles William Andrews, F.R.S., the President addressed him as follows :— Dr. ANDREWS,—The Council has awarded to you the Lyell Medal as an acknowledgment of the value of your numerous researches in Vertebrate Paleontology. Since your appointment to the Geological Department of the British Museum in 1892, you have made excellent use of the opportunities for research afforded by your official duties, and important contributions to our knowledge of fossil reptiles, birds, and mammals. You were soon attracted by the unique Leeds Collection of Oxfordian marine reptiles, and your studies of this collection eventually culminated in the two handsome volumes of the Descriptive Catalogue, published by the Trustees of the British Museum (1910-13), which must always remain a standard work on Ichthyopterygia, Sauropterygia, and Crocodilia. Your papers on the South American Stereornithes, on Rails from islands in the Southern Seas, and on Prophaéthon from the London Clay, are equally valuable contributions to our knowledge of extinct birds. Reports & Proceedings—Geological Society of London. 185 Your researches on the fossil mammals of Hgypt, many of them discovered by yourself, are still more noteworthy ; and your Descriptive Catalogue of the Tertiary Vertebrata of the Fayim (Egypt), published by the Trustees of the British Museum in 1906, began a new era in the history of mammalian life. Your demonstration of the stages in the evolution of the Proboscidea and of the relationship between the Proboscidea and the Sirenia, your description and interpretation of the strange Hocene genus Arsinoithertwm, and your recognition of the early differentiation of the Hyracoids in Africa are especially fundamental contributions to biological and geological science. I would further add that all your writings are characterized by remarkable thoroughness and insight into the meaning of the facts described. As your colleague in the British Museum during the whole period of your service, it gives me great pleasure to hand to you this medal, which the Council of the Geological Society could not have more worthily bestowed. Dr. Andrews replied in the following words :— Mr. President, —I wish to express my most sincere thanks to the Council of the Geological Society for the honour that it has done me in awarding to me the Lyell Medal, and to you, sir, for the too flattering terms in which you have made the presentation. Iam particularly pleased to have received this medal from the hands of one with whom I haye been associated for so many years. You will remember that, exactly twenty years ago, you yourself received this award from Dr. Henry Woodward, and that at the same time I received a moiety of the Balance of the Proceeds of the Lyell Geological Fund. If I have been able to accomplish something in Vertebrate Paleontology, it is mainly due to the fortunate environment in which I have found myself. An assistant in the British Museum possesses quite exceptional advantages, having free access to the great libraries and to the ever-increasing collections, and lastly, but by no means least, having many opportunities of making the personal acquaintance of workers interested in his subject. Having enjoyed these privileges, I feel that I have somewhat fallen short of what I ought to haye accomplished; but, although it is just now uncertain what the future may have in store for us, I hope that I may still have opportunities of doing further work such as will justify this award. The President then handed the Balance of the Proceeds of the Wollaston Donation Fund, awarded to Mr. William Bourke Wright, -B.A., to Mr. George William Lamplugh, F.R.S., for transmission to the recipient, addressing him as follows :— Mr. LAMPLUGH,—The Balance of the Proceeds of the Wollaston Donation Fund is awarded to Mr. William Bourke Wright, in recognition of his con- tributions to Quaternary Geology. After completing his geological studies under Professor J. Joly at Dublin University, Mr. Wright joined the Ivish branch of the Geological Survey, and came under the influence of yourself when you were engaged in working out the glacial problems of the Dublin district. He took part in the revision of the memoirs and drift-maps of the Dublin, Belfast, and Cork districts, and shared with Mr. H. B. Maufe the discovery of a continuous raised-beach feature older than the Glacial Period. He also observed this pre-Glacial rock-shelf or beach in the West of Scotland, showing that a general subsidence allowed the sea to enter the valleys along the coasts of the British Isles, almost at the present sea-level, before they were occupied by the ice. After some experience both in Scotland and in England, Mr. Wright returned to Ireland, where, as senior Geologist of the Irish Survey, he has. since been successfully engaged on the glacial geology of the Kenmare and Killarney district. Much of his leisure has been devoted to the preparation of an important work on The Quaternary Ice Age, in which he has made good use of his observations not only in the British Isles but also in Scandinavia. Impressed by the value of Mr. Wright’s researches, the Council will be glad if you will transmit this award to him, with its best wishes for the progress of the work which he has so well begun. 186 Reports & Proceedings—Geological Society of London. In handing the Balance of the Proceeds of the Murchison Geological Fund, awarded to Mr. George Walter Tyrrell, F.G.S., to Dr. Herbert Lapworth, Sec. G.S., for transmission to the recipient, the President addressed him in the following words :— Dr. LAPWORTH,—The Balance of the Proceeds of the Murchison Fund has been awarded to Mr. G. W. Tyrrell in recognition of his contributions to the petrology of South-Western Scotland. His keen petrographic insight was first shown in his description of the quartz-dolerite sills of Kilsyth. His results of most general interest to geologists are those connected with the Paleozoic alkaline rocks; for his investigation of Lugarite has added to petrology a peculiar rock-species and important evidence in favour of the differentiation of igneous rocks by the sinking of their heavier constituents. In several papers on the Auchineden Hills he has described their igneous rocks and their glacial and physical features; and in his recent account of the ravine known as the Whangie he has advanced conclusive evidence of its formation by earth- movements. As the Senior Assistant in the Geological Department of Glasgow University, and later also as Lecturer on Petrology there, he has done much towards the development of that school of geology. The Council hopes that this award may encourage and assist him in further research. The President then presented a moiety of the Balance of the Proceeds of the Lyell Geological Fund to Mr. Martin A. C. Hinton, addressing him as follows :— Mr. HINTON,—The Council has awarded to you a moiety of the Proceeds of the Lyell Fund in recognition of your researches on the British Pleistocene Mammalia, and as an incentive to further work of the same kind. Under circumstances frequently discouraging, you have for many years devoted yourself especially to the study of the Rodentia and the Insectivora, and have obtained a remarkable knowledge of the skeleton and teeth of certain groups which are most commonly met with among fossils. In this manner you have made discoveries with an important bearing on many problems of Pleistocene geology, which you have never failed to recognize. As one who has followed your work with great interest for several years, it gives me much pleasure to hand you this award. The President presented the other moiety of the Balance of the Proceeds of the Lyell Geological Fund to Mr. Alfred Santer Kennard, F.G.8., addressing him in the following words :— Mr. KENNARD,—It is particularly appropriate that the second moiety of the Proceeds of the Lyell Fund should be awarded to you, who have worked so long and so successfully with Mr. Hinton at problems of Pleistocene geology in the South of England. In the leisure of a busy life you also have made yourself thoroughly acquainted with a group of fossils, the Non-marine Mollusca, which are of fundamental importance in classifying and interpreting the various deposits in which they occur. Both alone and with Mr. B. B. Woodward you have published many interesting notes and lists of such Mollusca from Pleistocene and Holocene deposits in different parts of Britam. The Council desires to acknowledge the value of this work, and I have much pleasure in handing to you a tangible expression-of its good wishes. The President thereafter proceeded to read his Anniversary Address, giving obituary notices of Count Solms-Laubach (elected a Foreign Member in 1906), René Zeiller (el. For. Memb. 1909), Kdmond Rigaux (elected a Foreign Correspondent in 18938), and Michel F. Mourlon (el. For. Corresp. 1899), as also of the following Fellows: James Geikie (el. 1873), H. H. Howell (el. 1853), R. Lydekker (el. 1883, resigned 1915), C. Callaway (el. 1875, resigned 1906), A. Vaughan (el. 1900), O. A. Derby (el. 1884), W. Anderson Ls Lg & Proceedings—Geological Society of London. 187 i 1899), H. Kynaston (el. 1894), W. G. Adams (el. 1865), R. Assheton (el. 1886), Hon. Robert Marsham-Townshend (el. 1859), Sir Sandford Fleming (el. 1877), F. W. Millet (el. 1900), A. Dunlop (el. 1874) G. H. Hollingsworth (el. 1879), B. Holgate (el. 1877), W. Simpson (el. 1893), J. T. Hotblack (el. 1900), H. ‘Rote (el. 1890), D. A. Louis (el. 1909), H. S. Bion (el. 1911), W. J. Clunies Ross (el. 1882), and others. He also referred to the death of William Rupert Jones, late Assistant Librarian. The President then discussed the use of fossil remains of the higher vertebrates in stratigraphical geology. ‘The study of fossil fishes, to which he had referred in his Address of 1915, raised the question as to whether animals of apparently the same family, genus, or species might not originate more than once from separate series of ancestors. The higher vertebrates, which inhabited the land, might most profitably be examined to throw light on the subject; for the land has always been subdivided into well-defined areas, isolated by seas, mountains, and deserts, so that animals in these several areas must often have developed independently for long periods. Students of shells are unanimous in recognizing what they term homcomorphy, and trace immature, mature, and senile stages in the course of every race that can be followed through successive geological formations. Vertebrate skeletons, which have much more numerous and tangible characters, and approach senility in more varied ways, should afford a clearer view of general principles. Even among vertebrates the evidence that most concerns the geologist is not always easily interpreted. For instance, the Sparassodonta and horned tortoises of the Argentine Tertiary are ‘so closely similar to the existing Thylacines and the fossil Miolania of Australia, that they are still sometimes quoted as proving the former existence of an Antarctic Continent uniting the South American and Australian regions. On the other hand, they may be ‘merely survivors of cosmopolitan races at the two extremes of their former range, with certain inevitable (but not altogether similar) marks of senility. In making comparisons, indeed, it is no longer enough to distinguish the fundamental and merely adaptive characters of animals; it is also essential to note separately those characters which depend on the early, mature, or senile position of the particular animals in the evolving series to which they belong. Hitherto there seems to be only one case in which we have enough materials for forming a judgment as to whether a fundamental advance may occur more than once. Mammal-like reptiles are abundant in the Permian of North America and in the Permian and Trias of South Africa and other parts of the Old World. Recent studies have shown that all specializations in the North American forms are in the direction of higher reptiles, while all those in the South African forms are in the direction of mammals. Hence, although there is evidence of two possible sources of mammals, only one appears to have produced them. Among advances of lower degree, the origin of the monkeys or lower Anthropoidea may be considered. It is agreed that they arose from the Lemuroidea which were almost universally distributed over 188 Reports & Proceedings—Edinburgh Geological Society. the great continents at the beginning of the Tertiary era. They seem to have evolved separately in America and in the Old World, but the two series are very sharply distinguished, although they form one zoological ‘sub-order’. When isolated on the island of Madagascar, some of the same animals acquired a few peculiarities of the American, others of the Old World Anthropoidea, but never really advanced beyond the Lemuroid stage, merely becoming senile just before their extinction. Hence, the Lemuroidea evolved in three different ways, and the resulting groups are very easily distinguished. The study of the Tertiary Ungulata is especially important, because most of the groups arose either in North America or in the Old World, which were united and separated several times. It seems clear that, although each group probably originated but once in one particular area, its members soon diverged into several independently evolving series, each imbued with some definite impulse or momentum towards specialization in the same way in the course of geological time, only at different rates. There were thus, for example, several distinct lines of horses and rhinoceroses, but all from the same source. It is now well known that the characteristic South American Tertiary Ungulates arose in an isolated area, and many of their specializations are curiously similar to some of those observed among Kuropean Eocene and Oligocene Ungulata which soon proved abortive or ‘inadaptive’. They are, however, by no means identical. While so many changes have occurred during the evolution of the vertebrates, the persistence of characters and the strength of heredity in numerous cases are still as Petplexing as they were when Huxley first directed special attention to ‘ persistent types’. The President enumerated some illustrations. The ballot for the Officers and Council was taken, and the following were declared duly elected for the ensuing year :— OFFICERS (who are also ex-officio members of the Council) : President: Alfred Harker, M.A., LL.D., F.R.S. Vice-Presidents: Sir Thomas Henry Holland, K.C.I.E., D.Sc., F.R.S.; Edwin Tulley Newton, F.R.S.; the Rey. Henry Hoyte Winwood, M.A. ; and Arthur Smith Woodward, LL. D, F.R.S. Secretaries: Herbert Henry Thomas, M.A., Se.D.; and Herbert Lapworth, D.Se., M.Inst.C.E. Foreign Secretary: Sir Archibald Geikie, O.M., K.C.B., D.C.L., LL.D., Se.D., F.R.S. Treasurer: Bedford McNeill, Assoc. R.S.M. CouncIL: Henry Bury, M.A., F.L.8. ; Professor John Cadman, C.M.G., D.Se., M.Inst.C.E.; Professor Charles Gilbert Cullis, D.Sce.; R. Mountford Deeley, M.Inst.C.E.; Professor William George Fearnsides, M.A.; Walcot Gibson, D.Se.; Finlay Lorimer Kitchin, M.A., Ph.D.; John Edward Marr, M.A., Se.D., F.R.S.; Richard Dixon Oldham, F.R.S. ; Robert Heron Rastall, M.A.; Professor Thomas Franklin Sibly, D.Sc.; Professor William Johnson Sollas, M:A., Sc.D., LL.D., F.R.S.; J. J. Harris Teall, M.A., D.Se., LL.D., - F.R.S.; William Whitaker, B.A., F.R.S. II.—Epinsurexw GrotocicaL Socrery. February 16, 1916.—Dr. Robert Campbell, President, in the Chair. ““Some Obscure Factors in Coastal Changes.”? By Professor Thomas J. Jehu, M.A., M.D., F.R.S.E., F.G.S. Factors affecting the development of the coastline were considered under three headings—(1) Changes in the relative level of land and Correspondence—J. W. Evans. — 189 sea; (2) erosion; and (3) accretion. Since Neolithic man arrived in Britain, there is evidence of a submergence along the coasts of England and Wales and the Sonth of Ireland, and of an emergence along the coasts of Scotland and the North of Ireland. These movements took place prior to the time of the Roman occupation of Britain. Whether movements have taken place in still more recent times is somewhat doubtful, but there are slight indications of a subsidence in the extreme North of Scotland, and at one or two places on the coasts of England and Wales. Reference was made to the need of systematic observations being carried out by the Ordnance Survey to ascertain whether such movements are now in progress, and, if so, to what extent. Estimates were given as to the extent of erosion and accretion in the United Kingdom within recent years, and it was shown that more land had been gained by accretion and artificial reclamation than has been lost by erosion. But while the gain has been almost entirely in tidal estuaries, the loss has been on the open coasts. Further, the gains have been due not so much to the accumulation of material eroded by the sea as to the deposition of sediment brought down by rivers from their drainage areas. The serious erosion on the coasts of Holderness and of East Anglia were described and illustrated by views. While the chief agents of erosion are well understood, it was pointed out that there is a great lack of knowledge as to what takes place below the level of low water. Observations are needed regarding such questions as submarine erosion, the travel of material below the low-water line, and the movements of outlying sandbanks. There is much obscurity as to the limits of depth at which materials are moved on the floor of the submerged continental platform by waves of current action, or both combined; and again as to what depth the movement of detritus on the sea-floor is really effective in producing abrasion. The intermittent character of the erosion at many places on the east coast of England was noted as a puzzling fact. It may be due to an alteration in the point of attack of the sea on the coastline, brought about by the shifting of outlying sandbanks or shoals. . Another factor in erosion, the importance of which has been over- looked, is the action of rock-boring organisms. An account was given of the present state of knowledge regarding their work and of their effect on the sea-bed near Cromer. Little is known as yet as to the rate of boring, or as to the depth to which it occurs. CORRESPON DHNCE. DIFFERENTIATION IN IGNEOUS ROCKS. Sir,—Having occasion to refer to the report of my contribution to the discussion ‘‘Sur la différentiation dans les magmas ignés”’ at the Toronto Geological Congress, in the Compte Rendu (pp. 248-9), I find that through some typographical accident, which in the absence of a proof remained uncorrected, the meaning of one paragraph has been seriously obscured. 190 Obituary—Professor John Wesley Judd. After suggesting that the presence of a considerable amount of water in a magma might result in its separation in the liquid state into two immiscible portions, the lighter containing the greater part of the water and of the more acid and alkaline constituents, representing quartz and the alkali felspars, and the heavier consisting mainly of the basic constituents with comparatively little water, I continued: ‘‘Tt was to be expected that the character of the differentiation would depend on the amount of water present. If this were larger, one would expect a comparatively complete removal of the alkali felspar materials.’” [‘‘ With less water one may expect a greater amount of the alkaline material to remain with the more basic portion”’], ‘‘ and with further differentiation by other processes this would naturally give rise to a series of rocks of the alkali or ‘Atlantic’ type. This suggestion—it was intended to be nothing more—appeared to derive some support from the frequent association of rocks of this character with block faulting, while rocks of the normal or ‘ Pacific’ type were usually found within areas characterized by folding, where there was less facility for the escape of water to the surface.” The words in square brackets are those actually used in the first draft of the summary of my remarks supplied to the Secretary of the Congress. ‘hey were probably modified in the fair copy, but those appearing in their place in the printed text do not make sense. Indeed, the only meaning that might be extracted from them would be exactly the opposite of that intended, as shown by the context. A brief but correct version will, however, be found in my contribution to the discussion on a paper by Professor P. Marshall (Quart. Journ. Geol. Soc., vol. xx, p. 406, 1914). It is immaterial for the present purpose whether my suggestion with regard to the origin and distribution of the alkali rocks was well founded. I merely wish to have it correctly recorded. J. W. Evans. IMPERIAL COLLEGE OF SCIENCE AND TECHNOLOGY (RoyAL SCHOOL OF MINES). March 9, 1916. (Spsresay Ops Sg PROFESSOR JOHN WESLEY JUDD. Many friends and numerous old pupils will deeply regret the death of Professor J. W. Judd, who passed away at nis home in Kew on March 8. In 1905, when he retired from the Chair of Geology in the Royal College of Science, this Magazine published the story of his life, with.a list of his many contributions to science, so that it will now suffice to continue that story to the closing days. These were spent either at Kew or at a small house which he had acquired at Walmer; for he had ceased to travel, partly on account of his own health, since before retirement he had begun to suffer from a form of Obitwary—Professor John Wesley Judd. 191 deafness which is often associated with vertigo, and partly because that of one of his two children required constant watchfulness. His own physical trouble, which happily did not materially increase, was just sufficient to cause his gradual disappearance from scientific gatherings in London. Still, he was my guest in Cambridge at the Darwin Celebration in 1909, and it. was not till the outbreak of the present War that any serious failure became marked. Of that War he may be regarded as an indirect victim. Its horrors at the present and its ominous promises for the future were a bitter disappointment to a man of his sympathetic nature. The thought of them depressed his spirit by day and haunted his dreams by night. Rather more than a year ago he began to suffer much from neuritic pains, which often cramped his limbs and impeded his movements. A visit to Walmer during last summer sent him back to Kew in a more hopeful condition, but no long time afterwards he began steadily to lose strength, till at last he literally fell asleep. I can heartily endorse every word that a writer in this Magazine has already said in Judd’s praise as a geologist and a friend, alike to those of his own standing and to his pupils; for I have known him intimately for some forty years. We were Joint Secretaries to the Geological Society from 1878 to 1884, and he continued his services while I was President. We have met on many committees and as fellow-examiners, and in matters connected with the Funafuti boring, where he did a heavy piece of work in connexion with the examination and transport of the cores. We did not always quite agree on geological questions and matters of policy, but that never affected the constancy of his friendship. More than once he has gone out of his way to do me valuable service, and I have never met with a man who was less of a self-advertiser and self-seeker, or was more considerate of others. He was inflexible in taking the course to which, in his opinion, duty pointed; but his quiet, almost imperturbable, manner was united with a truly warm heart. Though during the last ten years new investigations had become practically impossible, he still made valuable contributions to geological literature. The most important of these, for it is needless to enumerate every ‘‘ chip from his workshop”, were the following: “Henry Clifton Sorby and the Birth of Microscopic Petrology ” (this Magazine, 1908, p. 193); ‘‘ Darwin and Geology,” an essay in Darwin and Modern Science (1909); The Coming of Evolution, published in the Cambridge Manuals of Science and Literature (1910); Zhe Students’ Lyell, his second, revised and enlarged edition of Lyell’s Students’ Elements of Geology (1911); and an obituary of Sir Joseph Dalton Hooker, contributed to Professor Watts’ Presidential Address to the Geological Society in February, 1912. Judd’s last communication to that Society was on March 25, 1914, when he gave a succinct account of the Island of Rockall as a preface to a paper on its unusual rock by Dr. H. 8S. Washington. All these maintained a high level, and the Coming of Evolution is a most attractive book, both from the writer’s intimacy with Darwin and the ‘ dauntless three”? who stood beside him in that conflict and from its remarkable literary grace. 192 Miscellaneous. As initiator and organizer of the system of instruction in geology at South Kensington, already so well described in this Magazine, Judd did a great work, for this system was then unequalled in Britain and has never been surpassed. On that point I can speak with confidence, since I acted for some years as his external examiner, and have had, in a similar capacity, considerable experience elsewhere. The results were admirable, and continue to be so under his successor, and it is therefore regrettable that, when Judd retired in 1905, his pension was calculated, on technical grounds, not from the date of his appointment to office in 1876, when he at once devoted ~ his whole time to the work, but from 1881, when that became obligatory. It is, however, still possible to mitigate the injustice, for such it really was, by means of a pension from the Civil List to those who survive him. His only reward was the barren honour of being nominated Emeritus Professor of the Imperial College in 1913. T. G. Bonner. MISCHILLAN HOUS.- —_—_@—___ Tar Crosine or NarronaL GxEoLogicaAL CoLLECTIONS. Although it is not the habit of this Magazine to intermeddle with politics it seems desirable to put on record Government action with regard to National Geological Collections. A full account of the action of the Government is printed in the Museums Journal for March, including a verbatim report of the speeches in the Lords, the Deputation to the Prime Minister, and the comments of the German and Austrian Press. The report by the Retrenchment Committee was very severely handled in the Zimes by ‘‘ A Biological F.R.S.”, and among the more noteworthy letters that appeared in that newspaper were those of Sir Ray Lankester, who commented on the ignorance of the political Trustees of the British Museum, and the letter of the Speaker of the House of Commons (himself a principal Trustee of the British Museum), a letter which completely justified Lankester’s biting satire. The final result is that at the British Museum (Natural History) the galleries of Fossil’ Mammalia and Reptilia and the Gallery of Mineralogy will be open to the public on Monday, Wednesday, and Friday ; the other collections of fossils will be closed continuously. But so long as sufficient staff is available any student can have access to the collections at the normal times by personal application to a member of the staff. As regards the Museum of Practical Geology, it is ‘‘ closed to the general public’’, but the Geological Survey Offices, with the Map Room and Library, which are approachable only through the Museum, are open as usual. Teachers with their classes are still permitted to have access to maps, photographs, and other illustrations of the Survey’s work. ‘« Parturiunt montes, nascitur ridiculus mus.” ‘wi mer OF BOOKS OFFERED FOR SALE ae se oe |) nO eee a AT THE NET PRICES AFFIXED BY DULAU & CO., LTD., 37 SOHO SQUARE, LONDON, W. Three Quarto Volumes of about 400 pages each, small 4to, and an Atlas of 66 pages of maps in colours, 133 193, bound in heavy paper cover. Price £5 5s. per set net. THE COAL RESOURCES OF THE WORLD. An Inquiry made upon the initiative of THE ee ee COMMITTEE OF THE TWELFTH INTERNATIONAL EOLOGICAL CONGRESS, CANADA, 1913, with the assistance of t GEOLOGICAL SURVEYS AND_ MINING GEOLOGISTS OF DIFFERENT COUNTRIES. EDITED BY THE GEOLOGICAL SURVEY OF CANADA. “The preparation of the monograph involved a large amount of special investigation in several of the countries from which reports were submitted, and the three volumes with the atlas of beautifully executed maps will serve as a fitting companion volume to The Iron Resources of the World.”’—Nature. BATHER (F. A.). Studies in Edrioasteroidea, I-IX. Reprinted, with additions, from the Geological Magazine, 1898-1915. London, 1915. . 8vo. 136 pages and 13 plates. 10s. BONHOTE (J. L.). Vigour and Heredity. London, 1915. S8vo. With coloured and uncoloured plates and diagrams in text. Cloth. 10s. 6d. CHILD (C. M.). Senescence and Rejuvenescence. Chicago [1915]. 8vo. pp. 480. Illustrated. Cloth. 16s. CRAIG (EH. H.C.). 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The Rare Earths, their Occurrence, Chemistry, and Technology. — a ; GEOLOGICAL MAGAZINE Monthly Journal of Geologn. WITH WHICH IS INCORPORATED SDA So 09 SO aed © 8 SS Ja ey OS IS a EDITED BY HENRY WOODWARD, LL.D... F.-R.S., &C. F.G.S., ASSISTED BY PROFESSOR J. W. GREGORY, D.Sc., F.R.S., F.G.S. Dr. GEORGE J. HINDE, FR.S., F.G.S. os THOMAS H. HOLLAND, K.C.1 E., A.R-C.S., D.Sc., F.R.S., F.G.S. DR. JOHN EDWARD MARR, M.A., Sc.D. (CAms.), F.R.S., F.G.S. DR. J. J. H. THALL, M.A., Sc.D. (Camp.), LL.D, F. = 8. F.G.S, PROFESSOR W. W. WATTS, Sc.D., M.Sc., F.R.S., VicE- Py tan? + Dr. ARTHUR. SMITH WOODWARD, F.RB.S., F.L.S., raat lasting ws %) MAY, 1916. ( OCT 211916 CONTENTS 4 I. ORIGINAL ARTICLES. The Petrography of Arran. By G. W. TYRRELL, A.R.C.Sc., F.G.S., University of Glasgow... A New Variety of Ammonite from the _ Lower Lias, Dorset. By Wyatt WINGRAVE, M.D. (Plate VIII.) The Crystalline Rocks of the Piémontese Alps. By C. 8. Du RICHE PRELLER, M.A., Ph.D., pa Ed By. Byes ck GS. ae a Sketch- _map. sae _ Tridymite and Quartz i in Icelandic Rocks. By LEONARD HAWKES, B.Sc. oe IX and 2 Text figures.) Further Notes « on the Land of Deep Corrosions. By F. KInGDOoN WARD, B.A., F.R.G.S. II, NovicEs oF Memorrs. By Wriesian Water in Manitoba. J. B. Tyrrell en os Ill. ae Dr. A. Strahan: The Coals of South Wales in reference to Anthracite. (With a Page-map.) The Mineral Resources of Great Britain .. The faeeres Pakconaic. pBlocaile ae Burma. Page 193 196 198 205 . 209 . 219 . 225 LONDON: DUBAU &CO., Lrp., REVIEWS -C. and E. M. Reid : Floras of the Dutch Baler: Geology of Western Australia Professor Bonney: On certain Channels teas Dee Se Geology of Copper Mountain, Kasaan .. Tertiary Mollusea, New Zealand .. 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TYRRELL, A.R.C.Sc., F.G.S., Lecturer in Mineralogy and Petrology, University of Glasgow. ‘{\HE phenomenon of which this paper treats occurs in a basalt | dyke exposed in a small quarry by the roadside north-east of Dippin, near the twelfth milestone from Brodick. This dyke runs from north-west to south-east, and is intrusive into the great teschenite (or crinanite) sill of Dippin. It is probably the one referred to in the Geological Survey Memoir on North Arran, South Bute, and the Cumbraes (1903), p. 119. It averages 12 feet in thickness, although it is extremely irregular, owing perhaps to the difficulty experienced in penetrating the tough, coarse, massive rock of the sill. The contacts are not plane, but abut against the crinanite in a very intricate manner, sometimes along vertical or horizontal joints, sometimes along irregular surfaces unconnected with jointing. Both contacts show thin films of tachylyte, which, as the rock is quarried, are left adhering to the irregular surfaces of the sill rock. Another dyke-like mass, 1 foot thick, is seen in the same quarry, and is doubtless an offshoot from the larger dyke. Within a foot of the northern contact of the larger dyke there are found enclosed several lumps of brown and black glassy rocks con- taining a few large white crystals of felspar. These lumps range from 1 to 8 inches in diameter, and are each surrounded by a thin film of tachylyte, while small clots of a black glass are to be found in their vicinity. Other xenoliths found near by consist of a medium- grained crystalline rock resembling the crinanite of the Dippin sill. These are larger than the glassy xenoliths and are quite evidently affected by heat. ‘They are also surrounded by a skin and sometimes clots of tachylyte. The Dyke.—The dyke belongs to a distinctive group of the Tertiary: north-west dykes, which appears to be abundantly distributed about the Clyde Estuary. These dykes have frequently been called ‘basaltic andesite’ or ‘andesitic basalt’, and are distinguished by containing beautifully fresh phenocrysts of anorthite or bytownite, in a ground-mass composed of laths of labradorite, augite frequently intergrown with enstatite or hypersthene, and an abundant mesostasis 1 The first two papers of this series appeared in the Gro. Maa., Dec. V, Vol. X, pp. 305-9, 1913. } DECADE VI.—VOL. III.—NO. V. 13 4 OCT 211916 % 194 G. W. Tyrrell—The Petrography of Arran. of dark glass. From their abundance in the island of Great Cumbrae, situated in the Firth of Clyde, it is proposed to distinguish them as the Cumbrae type of basalt. The Tynemouth dyke of the North of England appears to be an outlying member of the same series. In thin section the rock from the centre of the dyke shows small but rather numerous phenocrysts of plagioclase felspar which are occasionally euhedral, but are more often worn and corroded into curious irregular shapes. Whatever the shape, all the crystals possess a narrow marginal zone of different composition orientated similarly to the main mass. ‘I'he transition between the two parts is usually quite sharp. The measurement of extinction angles shows that the crystals are bytownite (Ab,An,) with marginal labradorite. There are also a few phenocrysts of fresh enstatite, showing a good positive biaxial figure in basal section ; and fewer still of a yellowish augite. The ground-mass is composed of zonal labradorite laths, intermixed with prismoids of augite and grains of iron-ore, with an abundant mesostasis apparently of a felspathic substance, crowded with black hair-like microlites, and probably representing a de- vitrified glass. This rock is an andesitic basalt or basaltic andesite generally similar to the Tynemouth and Cleveland dykes of the North of England. Other dykes of the same character, with slight variations in texture, amount of glass, or abundance of phenocrysts, occur in the vicinity, cutting the Dippin sill and the adjacent Triassic sandstones. Traced towards the margin of the dyke the rock becomes denser, and contains fewer and smaller felspar phenocrysts. A specimen taken 3 inches from the margin shows a beautiful variolitic texture in thin section. The felspars of the ground-mass are reduced to the size of large microlites, and are arranged in irregular radiating bundles or sheaves which involve numerous long prisms of augite and grains of iron-ore. At the actual margin the rock is tachylytic for a thickness of + inch. In thin section the glass is dark, opaque, and almost structureless, with only a few obscure microlites. It contains numerous small spherical amygdales of calcite, and a few small phenocrysts of labradorite with the usual rounded or irregular outlines indicating magmatic corrosion. The Xenoliths.—The great majority of the xenoliths are of pitch- stone. In thin section the bulk of this rock is seen to consist of a pure, almost colourless glass, in which hair-like microlites are aggregated into clots or patches, leaving -large areas of glass absolutely free from microlites. The phenocrysts are of euhedral quartz, orthoclase, and andesine (Ab;An,). The effects of the heat to which this rock has been subjected are striking. Of the three principal minerals orthoclase has suffered the most, andesine much less, and quartz hardly at all. The orthoclase in all cases shows some degree of fusion, which has occurred around the margins and along the cleavages, producing a yellow or greyish glass which contrasts with the lighter glass of the ground-mass. The resulting shapes of the crystals are highly irregular; occasionally the crystal ee ee ee eS G. W. Tyrrell—The Petrography of Arran. 195 is separated into two or three pieces by areas of fusion; but in extreme cases the crystal is represented by a ‘ ghost’ in greyish glass, in which only minute shreds of the original orthoclase have survived. The andesine crystals have apparently only suffered a little softening on the margins and fissuring in the interiors. The quartz has suffered least of all, as the crystals are only fractured. The fact that the broken pieces have occasionally floated away from one another is evidence that the glass of the pitchstone was rendered completely liquid by the degree of heat to which it was subjected. Kach xenolith is surrounded by a skin and sometimes clots of a black glass, which was at first regarded as a tachylyte of the same nature as that on the margins of the dyke. A thin section, however, shows that this material is really a colourless glass which is darkened by numberless lines, streaks, and patches of black dots, arranged with a perfect fluxional structure. The glass contains the same set of phenocrysts as the above-described pitchstone, but much smaller and fewer. Under a high-power objective the black dots which darken the glass are made out to be small, perfectly euhedral, hexagonal tablets of hematite, the larger ones translucent and of a blood-red colour. The difference between this rock and the pitchstone it envelops may be explained thus: the xenoliths have not only been perfectly fused, but the pitchstone glass has intermingled to some extent with the more basic glass of the basalt in which the xenoliths were carried up, the admixture of basalt glass resulting in the formation of swarms of hematite microlites. The flow-structure may have been imparted by a rolling motion of the xenoliths, due to differential velocity of the central and marginal parts of the basalt dyke during intrusion. The xenoliths are found within one foot of the margin, where movement would be retarded by cooling and viscosity on the marginal side, whilst proceeding at a faster rate in the more liquid interior. Conclusions.—The behaviour of the phenocrysts in the pitchstone xenoliths under the influence of heat gives some clue as to the .temperature of the basaltic magma in which they were immersed. The orthoclase was partially or wholly fused to a yellow or grey glass, andesine showed signs of softening around the edges, whilst quartz simply suffered some degree of fracturing. The most trust- worthy estimates of the fusion-points of rock-forming minerals have been made by A. L. Day and his collaborators in the Geophysical Laboratory at Washington.’ That of quartz (or rather silica, since quartz is unstable above 800° C.) is given as 1,625° C.; of oligoclase-andesine (Ab, An,) as 1,375° C. For orthoclase, however, we have to rely on the estimates of other experimenters.? The average of seven closely accordant estimates by Joly and Cusack, and Doelter, is 1,170° C. These figures are as would be expected from the effects produced by heat on these minerals. Orthoclase, which fuses at 1,170° C., has been converted into glass; andesine, 1 Clarke, Data of Geochenustry, 2nd Ed., U.S. Geol. Surv., Bull. 491, p. 279, 1911. 2 Iddings, Igneous Rocks, vol. i, p. 85, 1909. 196 Dr. Wyatt Wingrave—A New Variety of Ammonite. fusing in the neighbourhood of 1,375° C., has barely been affected ; quartz, fusing at 1,625° C., has only suffered fracturing. We may therefore conclude that the temperature of the basaltic magma during intrusion was between 1,170° C. and 1,375° C., excluding, as seems legitimate, any chemical reaction between orthoclase and the pitchstone glass. The ordinary basalt lava is fusible at about 1,100° C., and this is perhaps the ordinary temperature of emission at a volcano, although Daly believes temperatures of 1,200° C., or even 1,300° C., may prevail in the great volcanoes of Hawaii at periods of intense activity." The fusion of minerals and even rocks has been observed in basaltic magmas by Lacroix and others.’ Independent evidence of high temperature upon intrusion in the case of the dyke in question is afforded by its tachylytic selvages. These are due to very rapid marginal cooling, and the rate of cooling depends directly on the difference between the temperature of the country rock and of the magma. The occurrence of xenoliths of pitchstone in a Cumbrae type of basalt, which itself intrudes a sill of teschenite or crinanite, affords useful evidence as to the relative ages of these three groups of intrusive rocks. A pitchstone dyke with a felsitic centre cuts the Dippin crinanite near Torr an Loisgte, about 13 miles north-west of the quarry in which the xenoliths are found.s This dyke trends in a north-west direction, and would therefore, if produced, appear in the vicinity of the quarry, beneath the crinanite sill. It is possible that fragments of this dyke have been brought up by the basaltic magma. ‘The sequence of the three types in time is clearly, first the crinanite sill, then the pitchstone, and finally the Cumbrae basalt. Similar evidence from other parts of the island goes to show that the Cumbrae basalts were one of the latest manifestations of igneous activity in Arran, if not the latest. IIl.—A New Variety or THE AmmonitR Ca@ztocrrés DAV 41, FRoM tHE Lower Lis, Dorser. By WYATT WINGRAVE, M.D. (PLATE VIII.) UENSTEDT ‘ described three distinct varieties of Ammonites Dave, with nine illustrations. They all belonged to the y zone of Lower Lias :— 1. Ammonites Davai, whose tubercles are somewhat clavate and with unsymmetrical prorsiradiate ribs. 2. A. Davei enodis is continental. It is a small specimen without tubercles, with fine symmetrical and prorsiradiate ribs. 3. A. Davei nodosissimus is also continental. This variety shows nine large bullate tubercles on each whorl, with close, fine, and symmetrically disposed flexiradiate ribs. 1 Tgneous Rocks and their Origin, 1914, p. 212. 2 Tiacroix, Les Hnclaves des Roches Voleaniques, 1893, pp. 563-5. 5 A. Scott, ‘‘Pitchstones of South Arran’’: Trans. Geol. Soc. Glasgow, vol. xv, pt. i, p. 22, 1914. 4 Quenstedt, Die Ammoniten des Schwdbischenjura, 1885. Sate eee pS eee GEOL. Mae., 1916. Pratr VIII. G. F. Strawson, photo. COELOCERAS DAVQI, RECTIRADIATUM, var. nov. Lower Litas. GOLDEN Cap, Dorszr. = fp ey ie ree) t ‘y e lit ane t Dr. Wyatt Wingrave—A New Variety of Ammonite. 197 Hitherto the first variety only has been described as of English source. Last year, on following the eastward continuation of the Green Ammonite Beds to Golden Cap several fragments of Davai were found in the Red Band. One of these supplies a nearly complete specimen, which does not conform to either of the above varieties. It differs from 1 and 3 in several respects. The ribs are of finer texture, more numerous, never bifurcate, symmetrical in size and spacing, rectiradiate and showing no tendency whatever to a forward inclination, except the last few ribs near the aperture. In C. Davei the ribs are strongly prorsiradiate, unsymmetrical, and often bifurcate. The tubercles are much more numerous than in the orthodox Davez. They abruptly commence at the beginning of the penultimate whorl, and apparently adorn each rib as far as the inner- most whorls can be identified. In shape they are somewhat clavate, but not so prominent as in the ordinary Davav. In the photograph several of the ribs on the outer whorls appear to indicate a tendency to tuberculation or ‘ flaring’; this is due to unremoved matrix. The suture has not yet been exposed, although an area of an inch or more of test was removed from the outer whorl near its termination, showing that the body-chamber, like other forms of Davei, is evidently a long one occupying more than one whorl. The degree of involution is very slight, barely more than contact. Nearly the whole of the test is intact, and shows the characteristic russet colour of the matrix. (Plate VIII.) Suggested name.— Ceeloceras Dave, var. rectiradiatum (var. noy.). MorruotogicaL Drraits. Size.—Diameter 80 mm. Whorls.—Very slightly involute, polygyral (6), uncompressed, symmetrical increase in size and shape. #ibs.—Numerous, single (never bifurcated), rectiradiate, shallow, regular interspaced, uninterrupted at venter. Tubercles.—Numerous, small, clavate, on all the inner whorls, but outer whorl undecorated, non-septate. Umbilicus.— Shallow, open (concentrum- and latumbilicate). Venter.—Convex, cost uninterrupted. Suture.—N ot exposed. Distribution (source).—Red Band, Green Ammonite Beds, Lower Lias: Golden Cap, Dorset. STRATIGRAPHY. This specimen came from the ‘‘ Red Band ”’ of the Green Ammonite _ Beds, which at Golden Cap near Seatown forms its base, and is convenient of access from the beach. Below it is the well-marked ‘“White Band”, each having its attendant beds of clay. Here the limestone Red Band is scarcely 1 foot in thickness and occurs as a single layer, but Mr. Lang is of the opinion that further west it is probably double owing to weathering influences.! These beds yield a fair supply of Ammonites, chiefly in fragments among the clays. 1 Ww. D. Lang, ‘‘ Geology of Charmouth Cliffs’’: Proce. Geol. Assoc.; vol. xxv, pt. v, 1914. 198 Dr. Du Riche Preller—Crystalline Rocks of Piémont. Above are otstoceras, T. Loscombet, below are latecosta and varieties of liparoceras. The Red Band itself yields Davei and various striata. Complete specimens are confined to the limestone bands, for in the clays they are much. mixed and often only as fragments, casts, and moulds. Oppel included practically the whole of the Green Ammonite Beds in his Davet zone; but in England this should be restricted to the Red Band, although fragments of Davei are often found in the clays several feet from the Red Limestone. For the excellent photograph the writer is indebted to Mr. G. F. Strawson. Ill.—Tar Crystattins Rock Arnas oF THE PIEMONTESE ALPs. I. Sournern anp Wersrern Prémont. By C. S. Du RIcHE PRELLER, M.A., Ph.D., M.1.H.E., F.G.S., F.R.5.H. InTRODUCTORY. N continuation of the preceding paper (Gnor. Mae., April, p. 156) which, as a preliminary to the present one, outlined the new classification of the crystalline rock formations and the nomenclature of the pietre verdi of the Piémontese Alps, I now propose to briefly describe the principal pietre verdi areas with which I became familiar during a long stay on repeated occasions in Turin. This city, apart from its rich collections of the rocks and minerals of the Piémontese Alps, is a most central and convenient starting-point for examining the different valleys debouching into the plain of the Po from the magnificent crescent formed by the Maritime, Cottian, Grajan, and Pennine Alps, which, as seen from Turin, afford by far the most extensive and fascinating Alpine panorama in Italy. The principal pietre verdi areas lie more especially along or near the inner belt or concave eastern edge of the Alpine crescent, and include, among others, the following mountains and valleys which will be referred to in this and a subsequent paper, and all oe which form part of the watershed of the Po: — Range. Mountain. Altitude. Valleys. | m. Maritime | Montgioie 2,836 |Bormida, Tanaro, Corsaglia, Tllero, Vermenagna. a Argentera 8,397 | Gesso, Stura di Cuneo. Cottian Monte Viso 83,843 |Grana, Maira, Varaita, Po, Pellice, Germanasca. Be Rocciavré 2,778 | Chisone, Sangone. Grajan Rocciamelone 3,537 | Dora Riparia (Susa Valley). fs Ciamarella 8,876 | Stura di Lanzo: Usseglio, Balme, and Grande Valleys. “ Gran Paradiso | 4,081 | Orco, Soana. Hf Grivola , 3,961 | Dora Baltea (Aosta Valley), Cogne, Valsavaranche. - Mte. Emilius |: 3,559 | Dora Baltea, Buthier, Valpelline. Pennine Mte. Rosa 4,636 | (Ivrea Belt) @hinsellay Dora Baltea, Tourmanche, Gressonay, Cervo, Sesia. a a Dr. Du Riche Preller—Crystalline Rocks of Piémont. 199 Fig. 1, SKETCH-MAP of Crystalline Rock Aréas in Piédmontese Alps i (Southern and Western Piédmont.) i : Tose GQ. Paradéso etek ean cra} frees M.Cenis Y LY | R.d'Ambin pe in Te Z rejus 7 CZ ~ 2S we AS PNAS ‘ ly BA aurcore t,t ZZ Chabidke ra cs FZ | soins SE LolbikAZs “AViso BA i A ] nx. & nN be } w SoM Fo gene Mercarrtlo u : De orem ® Col brenda : f PV = pietre-verdi; gn = gneiss; gr = granite; _ms = micCa-schist; cs a calc-schist ; P = Permian; T = Trias. ‘Scale 1: 1,100,000. . ‘Del. D.R.P. 200 Dr. Dw Riche Preller—Crystalline Rocks of Piémont. Of the mountains enumerated, the Argentera and Gran Paradiso massifs, with a gneiss nucleus in each case, are the only ones which have preserved their original ellipsoidal, dome-shaped outlines, while most of the others, lying in the calc-schist and pietre verdi areas, are conspicuous pyramids whose precipitous flanks, pre-eminently those of Monte Viso and Grivola, were chiselled probably quite as much by atmospheric as by fluviatile or glacially abrasive action. The six principal pietre verdi areas, of which the first three will be dealt with in the present and the other three in a subsequent paper, are as follows :— I. In Southern and Western Piémont: (1) the Maritime Alps; (2) Monte Viso; (3) the Dora Riparia, Sangone, and Avigliana group. II. In Northern Piémont: (4) the Lanzo Valleys; (5) the Dora Baltea or Aosta Valley ; (6) the Lanzo, Ivrea, and Val Sesia group. J. Tue Maritime Arps Group. (Fig. 1.) 1. Montgioie Range.—The pietre verdi area between the Ellero, Corsaglia, Tanaro, and Bormida Valleys on the north side of the Montgioie range derives special interest from the fact that the deposits occur in the Permian and Triassic crystalline formations, already described in a previous paper,’ while further east, towards Savona and near Voltri in Liguria, similar deposits are intercalated in Triassic schists, and further west, along the French frontier, they appear in the cale-schist formation. Proof is thus afforded that the pietre verdi are not confined to any particular horizon, but are associated with both Mesozoic and Paleozoic formations. Some of the pietre verdi deposits on the northern slopes of the Montgioie range were already mentioned by Zaccagna’”; but their number and extent has more recently been considerably increased by Franchi,? who regards all the pietre verdi of the Ligurian, Maritime, and Cottian — Alps as links in the same Mesozoic horizon. The pietre verdi deposits between the Ellero, Tanaro, and Bormida Valleys, extending for about 30 kilometres along the lower hills from Villanova to Millesimo, are composed chiefly of lenticular masses of serpentinous, diabasic, and euphoditic rocks, the latter two largely altered to amphibolites and prasinites, all associated with Triassic crystalline and dolomitic limestone, in the Bormida valleys also with Permian schist, as already mentioned. In these, as also in the Lower Trias, occur frequent outcrops of laminated porphyric rock and masses of amphibolic schist often epidotic and garnetiferous, with abundant glaucophane.* West of the Montgioie range, in the border zone of the Maritime and Cottian Alps, and notably in the upper Grana and Maira Valleys, 1 “The Permian Formation in Piémont, Dauphiné, and Savoy’’?: GEOL. MAG., January, 1916, p. 7 et seq. 2D. Zaccagna, ‘‘ Alpi Marittime’’: Boll. R. Com. geol., 1889, p. 395 et seq. 3 §. Franchi, ‘‘ Zona Pietre Verdi fra 1’Ellero e la Bormida, Alpi Marittime ’’: ibid., 1906, p. 89 et seq. 4 The nomenclature used throughout this paper is that given in the preceding one, GEOL. MAG., April, 1916, pp. 156-63. ee eee - ; : F Dr. Du Riche Preller—Crystalline Rocks of Piémont. 201 similar euphoditic and diabasic masses occur in the calc-schist forma- tion, but intensely metamorphosed, the former to epidotic and chloritic prasinites with or without gastaldite (blue secondary hornblende), the latter to felspathic prasinites and amphibolites.' These pietre verdi masses bear close analogy to the euphoditic and diabasic, also variolitic masses with overlying serpentine in the cale-schists of Maurin and of the Chabriére Valley, near Pointe de Mary, about 30 kilometres further north-west, as also to those of the Mont Genévre group another 30 kilometres further north, and to those between the Ripa and Troncéa Valleys about 20 kilometres east of Genévre. From the occurrence of all these crystalline masses both of eruptive? and sedimentary origin on the northern and eastern flank of the Permian horizon, Franchi has rightly concluded that that formation separates the Trias into two distinct zones: an external one on the left, composed of the ordinary, fossiliferous limestone, gypsum, and cargneules or Briangonnais facies, and an internal zone, the crystalline and semi- erystalline facies composed of the cale-schists and crystalline and dolomitic limestone with pietre verdi.* 2. The Argentera Massif (Fig. 1).—This massif, also called Mer- eantour, is an oval-shaped ellipsoidal group of 60 by 25 kilometres in approximate length and width, extending west of Col di Tenda along the French frontier, and bordered on the north by the Stura di Cuneo Valley, which separates the Maritime from the Cottian Alps. The massif includes, besides Monte Argentera (3,397 m.) and Monte Matto (3,057m.) in the centre, some of the highest mountains of the Maritime Alps, e.g. Mercantour (2,775m.) and Monte Clapier (3,046 m.) at the south-eastern, and Monte Tinibras (3,032 m.) at the north-western end. The access to the central part is by the Gesso Valley from Valdieri, whose well-known hot sulphur springs rise in the upper valley, at 1,346 metres altitude, almost in the centre of the massif. The latter is, like the Dora-Maira and Gran Paradiso gneiss massifs, entirely free from pietre verdi on its surface; even the fringe of pietre verdi which surrounds those massifs is absent on its periphery. Zaccagna attributes this isolation of the Argentera massif to a great fault along the Stura Valley, which latter is, some 20 kilo- metres north-east of Valdieri, crossed by a succession of pietre verdi outcrops descending from the Maira and Grana Valleys towards Cuneo and S. Dalmazzo, and thence running along the base of the Montgioie range to Villanova and Millesimo. The Argentera massif consists, in the main, of three crystalline formations: a nucleus of primitive, glandular, large-grained, granitoid, 1 §. Franchi, ‘‘ Aleuni Metamorfisi di eufotidi e diabasi Alpi Occid.’’: Boll. R. Com. geol., 1895, p. 181 et seq. The transformation described in this important memoir applies equally to similar phenomena in all the other pietre verdi areas of the Piémontese Alps. In the massive and schistose amphibolites of the Grana and Maira Valleys, as also in Val Chisone, at Pegli, Liguria, and in the Tuscan archipelago, Franchi found the equivalent of the Californian mineral lawsonite, a secondary pseudomorphic plagioclase corresponding to the formula of hydro-anorthite felspar (Boll. R. Com. geol., 1898, p. 308). * The term ‘ eruptive’ is used in this paper in preference to ‘igneous’ as better corresponding to the non-intrusive character of the Piémontese rocks. 202 Dr. Du Riche Preller—Crystalline Rocks of Piémont. and eye-gneiss;1 a large area, about 12 by 10 kilometres, of granite intrusive in the gneiss nucleus; and asurrounding belt of great masses of small-grained gneiss and mica-schist. The primitive gneiss, and to a much lesser extent also the intrusive granite is traversed in all directions by countless thin veins of acid rocks, chiefly microgranite, aplite, quartziferous and hornblendic porphyrite, while the outer eneiss contains intercalated masses of both augitic and hornblendic diorite and of compact serpentine. These rocks, being here intimately associated with gneiss, are not pietre verdi with secondary elements ; but they show that the prototypes of the latter are not wanting even in the more ancient crystalline series. Professor Sacco regards the position of the gneiss and granite of the Argentera massif as reversed, viz. the granite not as intrusive, but as constituting the nucleus of the massif, enveloped by an enormous mass of gneiss intensely metamorphosed and of Permo-Carboniferous age*; but Franchi’s interpretation * is no doubt correct, the more so as there is no passage from gneiss to granite, and the intrusive character of the latter is beyond question. Moreover, the Triassic beds on the eastern as well as the Permian on the southern periphery of the massif overlie the gneiss with marked unconformity, thus pointing to a long interval of deposition and therefore to a considerable difference of age between the gneiss and the overlying younger formations. IJ. THe Monre Viso Grove. (Figs. 1 and 2.*) This area forms an elongated lenticular ellipsoid from south to north, about 40 kilometres in length and 2 to 6 kilometres in width, between the Maira Valley at its southern and the Pellice Valley at its northern end, while nearer the centre on its southern side it is cut by the Varaita Valley. In the centre itself, on the eastern side, rises the Po, which, although in its lower course it collects the drainage of all the rivers of the Piémontese Alps, is, in its upper torrential and cascade course, the shortest of all. 1 The term ‘ primitive’ gneiss is used throughout this paper in its strictly stratigraphical sense as the ‘fundamental’ substratum of all the more recent formations. 2 F. Sacco, ‘‘L’Age du massif de l’Argentére’’: Bull. Soc. géol. France, 1907, vi, p. 484 et seq. Also ‘‘Gruppo dell’ Argentera’’: Mem. R. Acc. Scienze, Torino, 1911, lxi, p. 457 et seq. 3S. Franchi, ‘‘ Osservazioni lavori geol. Alpi Marittime’’: Boll. R. Com. geol., 1907, p. 145 et seq. Among the excellent reports in the Boll. R. Com. geol., besides those already quoted in this and the preceding paper, are the following relating to the Cottian Alps :— 8. Franchi, ‘‘ Tettonica della zona pietre verdi del Piemonte,’’ 1906, p. 118 et seq.; ‘‘ Appunti geol. e petrogr. Monti di Bussoleno,’’ 1895, p. 3 et seq. S. Franchi and V. Novarese, ‘‘ Appunti geol. e petrogr. dintorni di Pinerolo,’’ 1895, p. 385 et seq. \ V. Novarese, ‘‘ Rilevamento geol. Valle Germanasca,’’ 1895, p. 253 et seq. ; ‘“Rilevamento geol. Valle Peliice,’’ 1896, p. 231 et seq. A. Stella, ‘‘Rilevamento geol. Valle Varaita;’’ 1895, p. 283 et seq. ; ‘* Rilevamento geol. Valle Po,’’ 1896, p. 268 et seq. 4 Figs. 2-4 will appear in the next part of this paper in June. Dr. Du Riche Pretler—Crystalline Rocks of Piémont. 203 The majestic appearance of Monte Viso—Pliny’s Mons Vesulus—is largely owing to the surrounding area of calc-schists having been considerably lowered by erosion which scooped out a socket-like depression round the base of the more resistant pietre verdi mass, and thus made the pyramid—the highest point of the Cottian Alps—all the more imposing. Close to it rise two similarly shaped but lower spurs: Visomut on its eastern side, and Visolotto grafted on its western flank, all three being in their upper or pyramidal parts composed entirely of pietre verdi. The same applies to Colle delle Trayersette (3,287 m.) at the western, to Monte Granero (3,170 m.) at the northern, and to Lobbie di Viso (2,990 m.) at the southern end of the group, which thus forms an enormous lenticular mass in the cale- schist formation, parallel to the Dora—Maira gneiss massif which separates it from the Po plain. 1. The Pretre Verdi Area of Monte Viso.—The least difficult access to the central part of the group for examining the pietre verdi series is from Barge (500 m.) to Paesana and thence up the Po ravine to Crissolo (1,385 m.) and to the summit of Monte Viso (3,843 m.), the four stages being (1) the eastern mica-schist zone to Paesana; (2) the Dora—Maira gneiss massif, in the ravine or chiusa of which the Po is joined by the torrent Lenta; (3) the western mica-schist, and then the predominant cale-schist formation with the quarried crystalline limestone beds of Crissolo; and (4) the pietre verdi up to the summit. The base of the Visomut spur discloses a great bank of serpentine. passing to schist, at least 500 metres in thickness, followed to the top by alternating banks of gneissiform euphodite and enphoditic and amphibolic schist, the former conspicuous by smaragdite, the latter by its epidotic veins, both of which minerals are largely prominent throughout the whole Monte Viso group. The depression between Visomut and Monte Viso, in which are embedded Lago Grande and other tarns, is composed of calc-schist, chloritic and serpentinous schist. From this point the succession of pietre verdi banks can be traced uninterruptedly to the summit of Monte Viso along the path leading from the Quintino Sella refuge (about 3,000 m.) up the southern flank. From the refuge, which is built on a felspathic euphodite bank, to the summit, the flank presents a series of alternating banks—as shown in the section, Fig. 2!—of euphodite, epidotic, amphibolic, actinolitic, and prasinitic schists from 200 to 300 metres in thickness, with smaller intervening banks of serpentinous schist. The euphodite, varying from compact to schistose, is largely of porphyric texture with greyish violet felspar and diallage altered to smaragdite. The amphibolic and prasinitic schists and their varieties predominate largely, and, together with euphodite, constitute the summit of Monte Viso, as they also do that of the almost perpendicular I This section is founded on Zaccagna’s great transverse section west to east of 70 kilom. from St. Paul in Dauphiné through the cale-schist formation, Monte Viso, and the Dora—Maira massif to Rocca Cavour in the Po Valley (Boll. R. Com. geol., 1887, p. 416, tav. ix). Franchi gives a similar section of the Monte Viso group at a lower level further south (ibid., 1898, p. 482, tay. ix; also Stella, ibid., 1896, p. 288). (For Fig. 2 see June Number.) 204 Dr. Dw Riche Preller—Crystalline Rocks of Piémont. peak of Visolotto. In all the alternating banks the gradual passage into, and compenetration with each other is very marked, and-so is more especially the tendency to chloritic decomposition forming serpentinous schist, which in contact with narrow bands of crystalline limestone imparts to the latter its greenish colour. The descent from Monte Viso may, on the southern side, be conveniently effected by the Forciolline gorge, and thence through the Vallante ravine and the Varaita Valley by Sampeyre and Venasca to Saluzzo in the Po Valley. In those deeply eroded ravines the calc-schist formation reappears in contact with amphibolie, prasinitic, and serpentinous schist. At the junction of the Vallante and Varaita Valleys the last-named schist predominates, and lower down the latter valley is replaced by alternating banks of cale-schist, serpentine, and chloritic amphibolite. 2. The Gneiss, Mica-schist, and Graphitic Area.—Parallel to and east of the pietre verdi area of Monte Viso runs, as already mentioned, the Dora—Maira primitive gneiss massif, about 60 kilometres in length and 5 to 10 kilometres in width, at an altitude of 1,500 to 2,000 metres, the visible thickness being about 700 to 1,000 metres. Its superficial continuity is, however, frequently interrupted by great intervening, overlying, or intercalated masses of minute, granular, and tabular gneiss, with which are associated masses of erystalline limestone, quartzite, steatite, and dioritic, amphibolic, and prasinitic rocks. ‘he primitive gneiss is the typical rock with large elements, glandular, often granitoid, and tourmaliniferous; the mica- schists, often garnetiferous, and the minute, tabular gneiss flank the primitive gneiss both on the eastern and western side. Of the gneissoid dioritic rocks associated with the minute and tabular gneiss, which latter reaches, e.g. in the Pellice Valley, a thickness of 1,500 metres, an intercalated mass 700 metres in thickness occurs near Barge; another, 1,000 metres, near Angrogna (Pellice); and again, in the Chisone Valley, another 1,500 metres in thickness, where the dioritic rock is associated with and altered to amphibolites and prasinites, including the ovardite of Fenestrelle. Both the tabular gneiss and the crystalline limestone, often associated with steatite, are extensively quarried on the eastern side of the Dora—Maira massif, at Vernasca, in the Varaita, near Luserna, in the Pellice, and near Malanaggio, etc., in the Chisone Valley, as are also the fissile, tegular, quartzite masses (bargiolina) of Monte Bracco (1,305 m.) near Barge. In the same mica-schist and minute gneiss horizon occur masses of graphitic rock with intercalations of graphite, which, flanking Monte Bracco on its western side, extend about 20 kilometres south, and about the same distance north of Barge. It is here, in the Pellice and Chisone Valleys, that the graphitic zone is. associated with the gneissoid dioritic rocks already mentioned. The whole mica-schist, minute gneiss, graphitic and dioritic zone is now assigned to the Permo-Carboniferous. 3. Summary.—Vhe Monte Viso and Dora—Maira areas may be grouped, in ascending order from east to west, viz. from Barge in the Po Valley to Crissolo and the summit of Monte Viso, in a distance of 20 kilometres, in four horizons as follows :— Leonard Hawkes—Tridymite in Icelandic Rocks. 205 Visible Altitude. depth. I. Primitive gneiss of Dora—Maira massif, glandular to granitoid II. Miea-schists, minute, tabular, and graphitic | 500-2,000 1,500 eneiss with quartzite, crystalline limestone, steatite, graphite, and dioritic rocks III. Cale-schists with crystalline limestone, pes and amphiboliec schists . z . 1,300-2,000 700 IY. Pietre verdi to summit of Monte Viso; : " serpentine and serpentinous schist ; epidotic amphibolites ; glaucophanic prasinites ; actinolitic, chloritic, - 2,000-3,800 1,800 and taleose schists; euphodites, gneissiform, porphyritic, and schistose 3,300 The total visible thickness between the extreme points—exclusive of the fall of level in the depression between the gneiss massif and the calc-schist horizon on the western flank of the former—is thus 3,300 metres. The fact that the mica-schist horizon flanks the gneiss massif on both sides, but on the eastern side along the base, viz. at a lower level, led Gastaldi to regard this reversal of the normal sequence as evidence of a zonal subsidence (sprofondamento), the more so as both formations dip below the valley floor and reappear about 6 kilometres east in the isolated outcrop of Rocca Cavour (460m.). Zaccagna, on the other hand, explained the phenomenon as an anticlinal retroflex fold of the gneiss massif from west to east. As a zonal fracture or subsidence, it bears close analogy to similar zonal phenomena in Northern Piémont, to which I shall refer in the sequel. (To be continued in our next Number.) IV.—On Trivymire and Quarrz arrer Trrpymire in IceLanpic Rooks. By LEONARD HAWKES, B.Sc. (PLATE IX.) LACROIX in his researches on volcanic rocks and their inclusions . has shown that tridymite occurs in two distinct forms, each produced under special conditions. ‘‘ Il est important de constater dans un méme échantillon l’existence de tridymite produite par deux modes de genése distincts ; qui lui ont imprimé deux formes différentes. L’une Welles est caracterisée par des cristaux épais, a macles binaires, elle a été formée par fusion; l’autre se présentant en lamelles ex- trémement minces, empilées a été produite par action pneumatolytique. Cette variété de tridymite constitue le dernier des minéraux dr rusiques formés, et elle résulte trés probablement de l’attaque a haute température dun résidue de matiére vitreuse trés siliceuse dont des restes peuvent étre parfois encore constatés directement’ (1, p. 387). Both forms occur in Icelandic rocks. In his description of the liparite of Hlidarfjall, Backstrom notes ‘‘sehr schonen Tridymite als letzte Bildung” (2, p. 661). Through the kindness of Professor Backstrom I was enabled to examine his 206 Leonard Hawkes—Tridymite in Icelandic Rocks, — rock sections, and a microphotograph showing the characteristic form of the tridymite is given in Fig. 1. The crystals are thick and frequently show binary twinning after (018). ‘Their resemblance to the artificial tridymite from the bricks lining the glass furnaces of Appert, Clichy, in France is obvious (ef. Fig. 2, 1, p. 331). The commoner form of tridymite, that of thin tables, is well shown in a breccia from Faskrudsfjord, East Iceland, consisting chiefly of fragments of an acid rock embedded in acid volcanic ash. This rock, 80 feet in thickness and intercalated in the Tertiary basalts, is exposed on the shore about a mile east of the town. The fragments of ash and lava contain phenocrysts of soda-microcline and soda- pyroxene in (a) a glassy perlitic base and (b) an aggregate of felspar quartz and pyroxene grains, respectively. In (a) the perlitic ground- mass is often weakly anisotropic, being made up of thin plates of tridymite. In (6) similar tridymite occurs together with quartz (described below) in cavities, and apparently in the groundmass. The nature and mode of occurrence of the two forms of tridymite of Hlidarfjall and Faskrudsfjord are in full accord with the theory of their mode of origin advanced by Lacroix. Quarts after Tridymite. The quartz to be described occurs in the rock of Faskrudsfjord. The pseudomorphs are of two types, both originating from the thin tabular form of tridymite. Type I.—Previously noted by Mallard (8, p. 162), Lacroix, and Geijer (4). The holocrystalline fragments of the Faskrudstjord breccia contain cavities filled with quartz, chlorite, and a small amount of a feebly double refracting mineral of low refraction, probably tridymite. A microphotograph of a cavity is given in Fig. 2. The quartz is of peculiar habit, forming a complex of lamellee branching out from one another at different angles. The network of laths in the cavity illustrated in Fig. 2 is comprised of two individuals, distinguished optically. While several lamellae may form one individual of common optical orientation, the laths forking without change in optical properties, one straight lath may be composed of many individuals. Fig. 3 shows another assemblage of laths comprising five individuals. This quartz is undoubtedly a paramorph of tridymite, and Geijer has described a similar occurrence in cavities in a pre-Cambrian quartz porphyry found as boulders in a moraine on Gotland. (See especially the photograph on p. 71, 4.) The quartz of the holocrystalline groundmass of the Icelandic rock is micropoikilitically developed, and without going into the question of micropoikilitic reticulating quartz which has been discussed by Geijer, it may be stated that it too, judging from its occurrence and association, is very probably a pseudomorph of tridymite. It is interesting to note that the soda-microcline pheno- erysts, which typically show inclusions of glass, sometimes contain lamellar quartz after tridymite (see Fig. 4), thus indirectly supporting Lacroix’s theory of the formation of tabular tridymite, ‘‘ de l’attaque & haute temperature d’un résidue de matiére vitreuse trés siliceuse.” Type II.—The paramorphs of Type I are characterized by the Leonard Hawkes—Tridymite in Icelandic Rocks. 207 retention of the lamellar form of the tridymite. In those now to be described the outline of the quartz is not that of the tridymite lamelle, being more or less rounded. ‘This type is well illustrated in a fragment 1 mm. in diameter, composed of twenty-three variously sized quartz grains, embedded in the Faskrudsfjord rock. Fig. 5 is a microphotograph of a part of the fragment, and Fig. 6 shows its outline and that of its component individuals. The quartzes are allotriomorphic with respect to one another, and a rapid glance conveys the impression of the usual granitic texture. On closer investigation, however, they are seen to have straight lines running Fic. 6.—A drawing of the aggregate of Fig. 5. The dotted lines are the traces of the former tridymite lamelle. through them, commonly in pairs, giving a rod-like appearance. Some of these lines are very distinct with a medium magnification, and they can be seen in Fig. 5, but many of them are only discernible using a high power and after continued observation. The lines discovered are dotted in in Fig. 6 ; none could be found in some of the quartzes. The structure is seen on slight movement of the microscope tube. The lines are dark and accompanied by ‘ white lines’, those forming a ‘pair’ or ‘rod’ deflecting in the same horizontal direction on movement of the tube. The lines obviously represent planes or cracks, each pair having a common inclination to the plane of section. 208 Leonard Hawkes—Tridymite in Icelandic Rocks. Sometimes several parallel lines have a common inclination clearly representing a section cut across several parallel imbricated lamelle. Tke lamelle join at varying angles, their junction often coinciding with that of the quartz individuals; though two joined lamelle may be contained in one individual. In one case three parallel lamelle of one quartz are joined at an angle to three parallel lamelle of an adjoining quartz, at the line of junction of the two individuals. Again, one straight lath may be contained in two quartzes. The lamellas commonly have a line of dark dust inclusions along their middle or surface. In general there is a tendency to coincidence in direction of the lamelle and the length direction of the quartz individuals. Fig. 7 is a drawing illustrating another homogeneous quartz filling a cavity and showing traces of a former complex of tridymite tables. Fic. 7.—Drawing of a single quartz individual, showing traces of an original complex of tridymite lamelle. x 150. It is clear that this granular quartz of 'ype II is merely a further evolution of that of Type I. Taking the lamelle in the granular quartz by themselves, their morphological and optical characters exactly correspond to those of the tabular quartz of Type I. In a complex of tridymite lamelle the paramorphism to quartz begins in certain of them, many going to form a single individual or one being changed into several, producing the structure of Type I. A further step is the paramorphism of the tridymite occupying the interspaces between these laths, and, probably through inoculation, the quartz formed is in optical continuity with that already present, giving rise to homogeneous granular individuals. The quartz shown to the left in Fig. 2 is obviously in the transition stage between the two types. The laths are the scaffolding on which the granular individual is moulded. The question arises as to whether we have been correct in regarding all granular quartz in igneous rocks as primary. The evidence is quite conclusive that the quartz individuals of Type IL in the Faskrudsfjord breccia are paramorphic after tridymite, yet in some of them the tridymite structure is only discernible with considerable difficulty, and in a few it is entirely eradicated. The importance of this fact in questions concerning the temperature of crystallization of quartz is obvious, and whilst it is unlikely that much granular quartz has originated from tridymite in the way Grou. Maa., 1916. Pratt IX. Fig. 5. Fic. 4. TRIDYMITE AND QUARTZ IN ICELANDIC ACID ROCKS. 1 F Kingdon Ward—The Land of Deep Corrosions. 209 described, it is desired to draw the attention of petrographers to the structure, in the hope of finding it to be of wider occurrence. In quartz-porphyries with micro-poikilitic structure the quartz phenocrysts are often surrounded by a network of quartz laths in optical continuity. Geijer regards the laths as paramorphic after tridymite, and suggests that their optical continuity with the phenocrysts may be due to inoculation by the latter. The discovery of the granular quartz suggested the possibility of these phenocrysts themselves being paramorphs of tridymite, and through the kindness of Professor P. D. Quensel, of Stockholm, I was permitted to look through Dr. Hedstrom’s slides described by Geijer. There were no traces in the phenocrysts of any structure similar to that in the Faskrudsfjord rock. Unfortunately there are no quartz phenocrysts in the Icelandic rock, and it is impossible to speak definitely yet on the question of phenocrysts and micropoikilitic quartz. I wish to express my thanks’ to Professor W. C. Brogger for permission to work at the Mineralogical Institute of the University of Christiania, and to Professor V. M. Goldschmidt for help and advice. REFERENCES. 1. A. LAcRorx, ‘‘ pat la tridymite du Vésuve et sur la genése de ce minéral par fusion ’’: Bull. Soc. Fr. Min., xxxi, 1908. hele Peay ‘“‘ Beitrage zur Kenntnis der islandischen Liparite’’ : Geol. Foren. Férhandl., No. 140, Bd. xiii, 1891. 3. MALLARD, Bull. Soc. Fr. Min., xiii, 1890. 4, P. GuigER, “ Poikilitic Intergrowths’’: Geol. Féren. Férhandl., Bd. xxxiv, Heft i, 1913. EXPLANATION OF PLATE IX. Fig. 1.—Nicols crossed. Section of the Hlidarfjall Liparite (Professor - Backstrém’s collection), showing an assemblage of thick twinned tridymite crystals. x 40 ,, 2.—Nicols crossed. Section of a fragment in the Faskrudsfjord rock, showing typical development of quartz lamelle—paramorphs of tridymite—in a cavity. The lamelle comprise two quartz individuals. The light streaky patches in the groundmass are micropoikilitic quartz. x 40. », °%.—WNicols crossed. Section showing a complex of quartz lamelle— paramorphs of tridymite—in a cavity in a fragment of the Faskruds- fjord rock, and optically resolvable into five individuals. x 120. ,, 4. Nicols crossed. From the Faskrudsfjord rock, showing a phenocryst of soda-microcline with albite and pericline twinning, and holding as an inclusion quartz lamelle, paramorphs of tridymite. x 120. ,, 98. Nicols crossed. From the Faskrudsfjord rock. Shows an aggregate of quartz grains with traces of tridymite lamellar forms. x 120. V.—Fortuer Groroetcat Nores on tHe Lanp or Drsp Corrostons.' By F. KINGDON WARD, B.A., F.R.G.S. N the Grotoercan Magazine for April, 1913,” I drew attention to certain features of the country forming the Yunnan—Tibet border. Further travels there in 1913 and through the Burmese hinterland 1 in 1914 enable me now to supplement and ‘extend those notes. 1 The rock specimens collected during my journeys of 1913 and 1914 have not been described. Their examination may help to throw some light on the problems here indicated. 2 ** Geological Notes on the Land of Deep Corrosions,’’ pp. 148-53, Pls. V and VI. DECADE VI.—VOL. III.—NO. V. i 14 210 F. Kingdon Ward—The Land of Deep Corrosions. Many travellers crossing Western China between Burma and Ssuchuan have regarded the endless parallel ranges which have to be erossed as spurs thrown out from the main Himalayan range or from the Tibetan plateau, at least as far south as Likiang. Thus Captain Gill writes: ‘‘The great plateau that extends over the whole of Central Asia throws down a huge arm between the Chin-sha-chiang (Yangtze) and the Lan-tsang-chiang (Mekong), gradually diminishing in altitude as it extends south. The northern portion of this arm partakes more or less of the character of the main tableland . . . this arm is not more than 35 miles wide in the latitude of Batang and . . . it is little more-than a ridge of mountains running due north and south between the two streams” (Zhe River of Golden Sand, vol. ii). West of Batang the summit of this divide is, as Captain Gill indicates, an undulating grass-land plateau cut up by streams flowing in shallow valleys, with lakes occupying hollows here and there, from 12,000 to 14,000 feet above sea-level; in appearance it closely resembles the grass-land country of North-East Tibet, on the Kansu border. But trom Atuntsi southwards to Likiang the divide narrows down to a mere rock wall. However, it is inconceivable that the Mekong—Yangtze divide was formed independently of the Mekong—Salween and Salween—Irrawaddy divides, which so closely resemble it in structure, as well as in their flora; if the Mekong—Yangtze divide is an arm of the great plateau, or a spur of the Himalayas, so too are its immediate neighbours, the Mekong—Salween and Salween-Irrawaddy divides. The same characteristics are repeated throughout the country to the east of Batang, though in a less sensational manner. The whole of the immense mountainous region lying between Batang and Tatsienlu and between the parallels of 32° and 26° partakes of the same nature, and though I do not know it at first hand the accounts of the few travellers who have been there emphasize the fact that it is a region of high parallel mountain ranges, often snow-clad, trending north and south, with rivers flowing south in deep narrow valleys between. However, in all this country there is no river to compare with those of the Yunnan—Tibet border, the Yalung being the only one of any size, though even beyond Tatsienlu the T'a-tu, and beyond that again the Min, also flow south. Captain Gill says of the country between Tatsienlu and Batang the day after leaving the former city: ‘‘ A few yards more, and reaching the summit of the Cheh-toh-shan we at length looked upon the great Himalayan plateau . . . and from this point, with the exception of a dip into the Yalung-chiang, the road is always at an altitude of 12,000 feet above the sea until the descent into the valley of the Chin-sha-chiang . . . ” (Zhe River of Golden Sand, vol. i1). The object of the present paper is to insist on the relationship and common origin of the physical features of the entire region from the Brahmapootra in Assam, across the sources of the Irrawaddy in the Burmese hinterland and the Yunnan—Tibet border, into Western China. There is no reason whatever to believe that this region may be regarded as a dissected plateau—that it was uplifted in its entirety at the same time as the Tibetan plateau and subsequently dissected F. Kingdon Ward—The Land of Deep Corrosions. 211 by rivers all flowing in one direction, leaving parallel mountain chains between. Why do the rivers all flow in one direction? Moreover, there is a significant curiosity about the courses of some of these rivers. The main lines of drainage run due south, parallel to the great ranges, since they cannot as a rule flow across them (hence the ranges antedate the rivers, or are perhaps contemporaneous with them). But why should the tributary streams throughout their greater lengths flow strictly parallel to the main rivers, finally turning abruptly at right angles to join them? This is true of the tributaries of the Mekong and Salween, and is even more pronounced in the case of the ’Nmai-hka. The explanation, I think, lies in the fact that the region is traversed by parallel lines of weakness, produced in a manner to be described presently, and it will probably be found that the tributaries turn at right angles to join the main rivers where a change in the character of the rocks occurs. Of the parallel rivers, the Mekong is the most easterly that continues its southern course to the sea. The Yangtze, after a series of remarkable loops, turns away to the east, thus snapping up all the rivers beyond which flow southward, and it has been suggested that it too, like the Mekong and Salween, once had an outlet to the south, through Indo-China. On what evidence that supposition is based I do not know, but a valley or series of valleys running southwards from Likiang, where the Yangtze abruptly ceases to flow southwards, to Tali-fu, now occupied by a chain of lakes and marshes draining south to the Mekong, of which the Tali-fu Lake itself is by far the most conspicuous, lends colour to the suggestion; there are also hot springs all the way along this shallow depression, and records of numerous earthquakes, leading to the belief that considerable crust movement has taken place here. The rocks are mainly sandstones, shales, and lhmestone—crystalline on the Tali-fu range. The big N-shaped bend of the Yangtze, at the end of its southern journey, just before it definitely sets out eastwards towards the Japan Sea, in the course of which it cuts diagonally across the Likiang range, not flowing round it as is shown on the maps, is peculiar, but by no means unique in this region. Here I need only remark that the fact of the river cutting across the range suggests that this portion of that river at least existed prior to the uplift of the lofty Likiang range; but it was not then necessarily the source stream of the Yangtze as we now understand that river. It is much more likely that the Chin-sha-chiang (reserving this name for the southward- flowing upper portion of the Yangtze) did actually continue southwards past Likiang, being subsequently beheaded by the upper course of the eastward-flowing portion cutting back westwards; the southern portion of the Chin-sha-chiang, being thus isolated from its source, ultimately disappearing. This would account for the abrupt change of direction of the Yangtze, but not altogether for the extraordinary double loop into which it bends itself, unless we suppose that the western loop was originally a tributary of the independent Chin-sha, the water of the latter being eventually diverted through the channel of the former to join the Yangtze. At any rate this peculiarity is shared by at least three other rivers of 212 F. Kingdon Ward—The Land of Deep Corrosions. this region, namely, the Yalung, the Dayul River (or Wi-ch‘u), and the Ngawchang-hka, while the upper portion of the ’Nmai-hka attempts a similar evolution and achieves a double bend, each half of which is less than a right angle. By the pinching of the rivers between rocks subjected to two sets of earth mevements acting at right angles to each other, in some cases actually buckling the strata, and to cutting back, owing partly to differences of rainfall on the two sides of a mountain range and partly to differences of level and of grade in the river-beds, which has gradually brought rivers originally belonging to separate hydrographic systems into contact, I imagine the whimsical courses of these rivers to have been evolved from simple courses. Whether this explanation be right or wrong, there can be no doubt that the several rivers which exhibit this phenomenon of reversed flow owe it to a common cause, and not to some chance freak in each case. It may be asked, what became of all the rain-water which must have fallen on this country previous to the west to east movement which, by cutting across and breaching the long axis of the great Asiatic divide, allowed the parallel rivers to drain southwards? ‘The answer is, much of the region was then occupied by vast lakes into which the water was poured. In the case of Hkamti—Loong, to be. referred to presently, at the sources of the Mali-hka (or western branch of the Irrawaddy), it is sufficiently obvious that this plain was once occupied by a lake, and again much further east we have an . ancient lake bottom in the ‘red basin’ of Ssuchuan, now the fertile Chengtu plain. But there is proof in the sandstones, slates, and lime- stone of the border country itself that most. of it was once under water. Much of the Mekong—Yangtze divide, for instance, is capped by limestone now raised 18,000 or 20,000 feet above sea-level, and the same rock reappears on the ranges to the west. North of Likiang we cross plateau country partially occupied by insignificant lakes, surrounded by sandstone or limestone ranges from the bases of which well up hot springs. But whereas the Hkamti plain is only 1,200 feet above sea-level, with parallel ridges of sands and clays enclosing organic remains still intact, rising 3,000 or 4,000 feet higher in the south, the old sea or lake bottoms east of the Yangtze have been pushed up into plateaux 8,000 to 12,000 feet above sea-level, and regional metamorphism must have obliterated any organic remains which may once have existed. Whereas the isolated lakes of Tibet are drying up, those of the Yunnan—Tibet border country have been drained. As already remarked, this border country has, in my opinion, been subjected to two sets of crust movement acting approximately at right angles to each other in such a manner that the hydrographic system set up during the first phase, at a later period became involved with and largely obliterated by that resulting from the second phase ; further complications were gradually introduced by the cutting back of either the primary or the secondary rivers, but especially by the former, according to local circumstances. During the first phase the Himalayas and the main backbone of China, separating the Yangtze and Yellow River basins, were raised up; during the second, a ae ae ae a F. Kingdon Ward—The Land of Deep Corrosions. 2138 the north and south trending parallel ranges which lie between Assam and Western China, though the Himalayas may have and probably did receive their last and greatest uplift (in Tertiary times) at a subsequent date. During the period of the first phase the region we are considering may have appeared somewhat as follows: (1) The Himalayas, either continuous with, or at least throwing out spurs to, the main divide of China (a consideration of the distribution of plants on the Himalayas and in Western China leads to this conclusion). (2) A great lake or system of lakes stretching throughout the present headwaters of the Mali-hka westwards into Assam, and covering thousands of square miles. (3) A region of great lakes and volcanic activity in Western China. (4) A number of rivers flowing into these rivers from the west, of which the upper courses of the Brahmapootra and Salween may have existed more or less as at present, eventually becoming involved with rivers consequent upon the second phase. At this time the Irrawaddy can have had no existence, nor probably had the Mekong. The Yangtze, however, flowed eastwards from the neighbourhood of the Chengtu plain, then a vast lake; its present upper course (distinguished as the Chin-sha-chiang) did not exist, and the same applies to the lower course of the Salween. The second great phase now seems to have been initiated by a crust movement from west to east, accompanied by the irruption of vast masses of granite. It may be thata lateral shifting of the Himalayan axis eastwards accounted for this, or perhaps it was due to a natural shrinking and settling of the crust; but whatever the cause, the parallel ranges to the east were those first formed, the western ones being pushed up later (the glacial phenomena and the distribution of flora on the parallel divides show this). The result of this second earth movement was to break the continuity of the Sino-Himalayan axis, and start rivers flowing southwards through the breach. Thus arose the Mekong and the lower course of the Salween from about latitude 29°, while the draining of the Hkamti-Assam country gave rise to the Irrawaddy. At this time too the Chin-sha may have flowed southwards past Talifu to the sea through Indo-China. The parallel divides were then much lower than at present, and the monsoon rains swept on into Western China, where there were great glaciers. Meanwhile the rivers of the old system were rapidly cutting back, with the result that the Yangtze eventually tapped the Chin- sha, while the lower and upper courses of the Brahmapootra, cutting down as the Himalayas rose, became united. All this time the parallel divides were being slowly elevated, gradually pushed up one by one from the west, but the probability is that they had attained no great elevation till the present hydrographic system was established, and there is reason to believe, from a consideration of the glacial phenomena on the Mekong-Yang gtze and Mekong—Salween Tease matter which requires separate treatment—that they are still rising. I have stated my belief that the parallel divides, with their intervening valleys, were formed by pressure from the west—that is to say, that the region is a series of anticlines and synclines; and on 214 F. Kingdon Ward—The Land .of Deep Corrosions. the whole it appears to be so. But the gorges in which flow the ’Nmai-hka, Salween, Mekong, and Chin-sha are not simple synclines deepened by erosion; they are more in the nature of rifts, gashes, or possibly faults produced by some other agency. If we cross all the valleys and mountain ranges, starting from the Brahmapootra, and travelling eastwards, keeping always in the same latitude, we shall find that as we pass from one valley to the next, we are gradually ascending, and also crossing successively higher mountain ranges between them, till the maximum average height is reached on the divide separating the Mekong from the Chin-sha for the short distance these rivers flow parallel to one another. The Mekong—Yangtze divide, however, is not the most snow-clad, for being protected from the monsoon by rain-screens to the west it receives only a fraction of the precipitation which falls on the western ranges, exposed to the full onslaught of the monsoon. Thus the entire region from the Brahmapootra to the Yangtze, in about latitude 28°, presents the appearance of a hugh bulk of rock, crystalline in the east, inclined from west to east, and trenched, riven, split asunder again and again from north to south. Now: how are we to account for the fact that the river beds from west to east, irrespective of volume and velocity and therefore of their erosive powers, namely, in order the Brahmapootra, Mali-hka, ’Nmai-hka (western and eastern branches of the Irrawaddy re- spectively, the latter being the maz stream), Salween, Mekong, and Chin-sha (Yangtze), lie at successively higher and higher levels? The problem is complicated by the fact that the rivers are of different ages, the Irrawaddy evidently being the most recent, while the Chin-sha is probably the oldest. The regularity of the ascent is not due to a progressive decrease in the erosive power of the rivers, due either to.a decrease in grade, to a decreased volume of water, or to any difference in the composition of the rocks over which they flow. The Mekong is a bigger and swifter river than the ’Nmai-hka, but it flows:at a higher level by some 2,000 feet. The Salween has a bigger volume of water than the Mekong, but flows over 1,000 feet below it. We cannot ascribe the phenomenon to chance, and the only explanation seems to be that the country realty does represent an inclined block of strata; and unless it has itself been planed down and carved out in this way, which is what we are endeavouring to show that it has not, and that it never existed above water except as a series of parallel ridges and valleys, we are almost forced to the conclusion that it must have been pushed bodily up over an inclined plane of older rock which it now overlaps. This sorts well with the belief, founded on a consideration of glacial phenomena and floral distribution, that the ridges were pushed up one by one from the west, by a lateral movement of the Himalayan axis. If such bodily movement of the mass did take place, it is easy to account for the rifts in which the rivers now flow, by fracture. If the pressure which gave rise to the original underlying synclinal structure was sufficient also to force this huge mass bodily up an inclined plane of older strata, sloping gently down to the west, at less than a degree,* 1 If the slope from the Chin-sha Valley to the Brahmapootra were uniform, it would be, in round numbers, about 1 in 3,000, or a slope of 20 seconds. =) F. Kingdon Ward—The Land of Deep Corrosions. 215 then any cessation or diminution of that pressure might allow the overlaying strata to sag back. The result would be that on the steeper slopes—for the slope from west to east is manifestly not uniform—the massive anticlines, dragging on the synclines, would cause the latter to crack, and rifts such as the parallel rivers now occupy would take the place of simple anticlines, accounting at the same time for the differences of level at which the rivers flow. The rifts once formed would be deepened by erosion, the valley walls being protected by the aridity enjoyed, which is itself increased automatically by the up-valley winds. It is, however, evident that these aggravating factors alone are not sufficient to account for the rifts in the first instance, since the Salween, south of latitude 28° in a monsoon region, flows through a very narrow valley, the rocks in the bed of which in all respects resemble those further north, and in places through gorges modified by the heavy summer rainfall; still more does the upper ’Nmai-hka (or Taron as it is now called) flow in a gorge, though the region is drenched with rain almost all the year round, Or, we may account for the rifts, and perhaps also for the marked differences of level, not by any lateral movement of the Himalayan axis, but by the elevation of that range itself, setting up a great tension strain at right angles in the adjacent crust, causing a sequence of parallel rifts to appear during the second phase referred to above, followed by an irruption of molten rock along the lines of weakness. - Lines of volcanic activity can be followed southwards from Batang through Yunnan (‘I‘engyueh volcano), Burma (Popa), the Arrakan Hills, and the Andamans (Barren Island), to the Indies, where the voleanic forces are at present concentrated, having forged southwards like a line of fire. In the case of a tension strain like that, the region most affected would be that nearest the seat of force, that is in the west nearest the Himalayas, where the broadest and deepest valleys would be formed; the least affected would be those furthest away, in the east, which would consequently be narrowest and highest. But while the rift formation may be due to this cause, and not to any pushing of the crust up a gently inclined plane with subsequent sagging back, it does not affect the synclinal origin of the great breach in the Sino-Himalayan axis, and the successive elevation of the parallel divides, the most easterly being those first elevated. This I now regard as proved from botanical and geological evidence. It will be noticed that there is a tendency for the river valleys not only to lie at higher elevations, but also to become narrower, so far as is consistent with their different powers of erosion, as we go eastwards. Thus the Brahmapootra valley, once the Himalayan axis is cut across, is broader and flatter than that of the Mali, and the Mali than that of the ’Nmai-hka. There is probably little to choose between the gorges of the upper ’Nmai-hka (Taron), the Salween, and the Mekong, as regards breadth,’ but the Yangtze valley is rather broader, the river itself being quite twice as broad as the Mekong. If no disturbing factors intervene the western rivers will eventually tap the eastern, owing to the cutting back of the tributaries 216 F. Kingdon Ward—The Land of Deep Corrosions. on the rainy sides of the several divides and the gradual shifting of the watersheds eastwards. This is inevitable. Thus the ’Nmai-hka will tap the Salween, and the Salween the Mekong, south of latitude 28° (the southern limit of the arid region on the former river). The Mali might tap the ’Nmai—the watershed hangs nght over the latter river at present, and the former will then become the main stream of the Irrawaddy, the ’Nmai disappearing; but an elevation of the Salween—Irrawaddy divide, by further concentrating the monsoon wind currents within the Irrawaddy basin, might prevent this by levelling up the present unequal distribution between the Mali and the ’Nmai; but it would also curtail tapping operations further east, south of the arid region, just as they have been stopped in the arid region itself, where the rivers grind out their gorges in isolated grandeur, indifferent to the freaks of their neighbours because independent of water save from the distant glaciers of Tibet. It may be that the Mali has already tapped tributaries once flowing to the ’Nmai, and that it is gradually stealing all its waters on that side; certain it is that no rivers flow to the’ Nmai-hka from the west, and whereas we reached the crest of the Mali-’Nmai divide the second day after leaving the latter river, an endless series of ridges and valleys had to be crossed, occupying nine days, before the Mali was reached. We come now to a brief description of the rocks in the valleys from the Yangtze to the Mali-hka, and on the intervening ranges in about latitude 28°. In the Yangtze valley slates and schists were noticed above, on the left bank, limestone below, but crossing to the right bank and ascending the Mekong—Yangtze divide the order was reversed—first schists, then limestone, after which came an outcrop of granite ; altitude 9,000-10,000 feet. All these rocks were highly tilted, sometimes almost vertical, the schists crumpled; dip varying, but approximating to N.E. The summit of the divide is capped by limestone and a red grit, probably arkose; the former sometimes cropping out in irregular cavernous bosses. Granite and schist also crop out in places, dip E.S8.E. at angles varying from 45° to 90°; altitude 15,000-17,000 feet. Descending to Atuntsi we find chiefly mica-schists, and higher up limestones and slates. Atuntsi lies in a depression which is evidently a syncline. To the west rises a bulky outlier of the main divide, 15,600 feet above sea-level, composed chiefly of slates, with curious pillars of limestone cropping out on its east and west faces. In the Mekong valley itself, purple and green slates are seen in the river bed, always standing on edge, and the same in the bed of the Salween ; the dip seems to decrease as one ascends. In a gorge of the Mekong just south of Atuntsi we pass from north to south through (1) vertical slates striking N.N.W., (2) granite, (3) lime- stone (?) ina few miles. Just south of the last is an outerop of coral limestone on the river bank. In the Mekong valley the schists and slates are everywhere almost vertical, the strike varying from N.N.E. to N.N.W. Altitude 7,000—9,000 feet. At 10,000 feet on the Mekong—Salween divide the schists and slates met with were vertical, striking almost due south, giving a succession F. Kingdon Ward—The Land of Deep Corrosions. 217 of narrow gullies on the main spurs, separated by razor-edged walls of rock standing out like ribs. The Mekong—Salween divide is here capped by granite, with outcrops of grey slate, instead of by limestone. Further north are various metamorphic rocks. Altitude 15,000— 17,000 feet. On the main spurs a succession of broken anticlines can sometimes be traced, causing the crests of the spurs, which are very steep-sided, to be jagged like a saw. Conglomerate was seen in one place at 17,000 feet. In the valley of the Wi-ch‘u, which is crossed twice before the Salween is reached, limestone and schists, dipping north at high angles, are met with. In the Salween valley the rocks are mostly limestone and granite in the north (i.e. north of Atuntsi), limestone, slates, and schists further south. The river cuts its way through remarkable gorges of granite and limestone, in some places crystalline, and at one place there are conspicuous scarps of the latter rock, like old river gorges, a thousand feet or so above the river. The summit of the next range to the west, the Salween—lrrawaddy divide, I have not yet crossed in this latitude, though I have several times seen its snowy peaks; but a hundred miles further south the great bulk of itis granite, with conspicuous cliffs and peaks of limestone cropping out lower down on the Burma side, and the same vertical slates reappearing in the bed of the ’Nmai-hka at least as far north as latitude 27°; still further north it appears to flow, like the Salween, through granite gorges. Leaving the ’Nmai valley and continuing westwards to Hkamti- Loong (latitude 27°), we pass from the igneous rocks of the great mountain ranges to laterite and clays as the plain is approached, and finally to sands and alluvium on the plain itself, overlying a hard conglomerate which contains rolled pebbles of many igneous rocks. The plain is divided by three conglomerate! terraces of varying breadth, rising one above the other from the river and trending in a more or jess north and south direction; they appear to be old river terraces, but their discussion is irrelevant here. Southwards of Hkamti-Loong we find in sequence fia north to south the following: (1) Gravel interstratified with sand, often iron- stained and showing current bedding; in places converted into conglomerate by the “weight of superincumbent rock and the infiltra- tion of water carrying iron salts in solution. (This is well seen in a nulla, the ‘conglomerate nulla’, three marches south of Hkamti.) I will digress here for a moment to comment on these interstratified sands and gravels. One cannot look at the upper Mekong in summer, its red flood hurrying along sticks and branches, and at the same river in mid-winter, its shrunken waters blue as the Mediterranean, without perceiving that a river which is largely fed by glaciers and melting snow, or one which flows through a region with marked dry and rainy seasons, may lay down strata of two distinct ty pes. Summer and winter deposits may in such case be as sharply demarcated as the ? The conglomerate is not solid right through, but forms an irregular ‘ pan’ at varying depths. 218 F. Kingdon Wurd—The Land of Deep Corrosions. - annual rings of summer and winter wood in a tree trunk, and may be put to the same use, namely, to determine how many years it has required to build a certain thickness. Summer layers would be characterized by greater thickness, coarser material, and plant debris, winter layers by sand and mud (glacier mud) without plant remains. In the case of a very big river flowing to the sea through a country the climate of which was not uniform, these results would be more or less vitiated owing to other causes, namely, (1) the creation of a reservoir of material at the mouth of the river, and (2) the effect of tides in sorting and delaying the deposition of material; moreover, the lower course of such a river is invariably sluggish and incapable of moving more than the finer materials of denudation. ‘Thus, even if the sediment was deposited as quickly as it arrived, no reserve accumulating, the uniformity of the material in suspension and the selective influence of the tides would effectually mask any classi- fication into summer and winter strata based on the appearances of the river in its upper course. Thus no such sequence would be detected in the case of such rivers as the Yangtze and Mekong, in spite of arguments founded on their appearance in the region of the parallel rivers, for these rivers are always muddy at their mouths, where there are’great reservoirs of silt. But in the case of a river, glacier- fed or otherwise, pouring into a big lake in the monsoon region, if the river is not too long, and especially if it derives much water from melting snow in the spring, seasonal deposits might be conspicuous, and it is to such seasonal deposits that I ascribe the interstratified sands, gravels, and leaf beds of the Hkamti basin. To continue the enumeration of strata passed between Hkamti-Loong and Myitkyna, we have, after the sands and gravels: (2) silver-grey (due to the presence of white mica flakes), buff, and reddish sands with rounded quartz pebbles; friable earths; argillaceous sandstones; blue clays, and grey claystones, with leaf beds and nodules of iron pyrites. The materials are coarser in the north, gravels, conglomerates, and sands, finer in the south, claystones and friable earths, showing that the rivers flowed into the lake from the north. The numerous native iron-mines in this region probably owe their origin to the accumula- tions of vegetable remains. South of the Hkamti plain these soft rocks have been thrown up into a series of ridges running parallel to the river and to one another, from 3,000 to 5,000 feet above sea-level, cut across by rivers flowing from the main divide (the Irrawaddy-— Brahmapootra divide, or further south, the Irrawaddy—Chinwind divide) in the west. 8. Crumpled mica-schists, produced from sandstones and giving rise to the same friable red earth (or clay) as is derived from the sandstones further north—in the bright sunlight this red earth is a burnt-ochre colour, and a beautiful feature of the scenery, where the dense jungle allows of its becoming visible; and bluish slates. The direction of dip varies between south and east, being generally about 8.E. or E.S.E., at angles varying from 30° to néarly 90°. 4. In the bed of the ’Mali-hka just above the confluence, dark grey slates with quartz veins, dipping east at nearly 90°. These slates probably underlie the lake series, and seem to be identical Notices of Memoirs—Artesian Water in Manitoba. 219 with the slates in the beds of the Mekong and Salween further north (i.e. in the north-east) and the oldest rocks in this region. It will be readily recognized how complicated is the geology of this region and how difficult it will be to unravel, not only on account of the vast extent of country involved and the physical difficulties of travel, but also owing to the alterations and displace- ments of the strata consequent on the great irruptions of granite, which is found from the river-beds, 6,000 feet above sea-level, to the erests of the Mekong—Salween divide at 18,000 feet, and to the fact that the Burmese hinterland is covered with impenetrable jungle. Tosumup. Everything in the arrangement of the rocks throughout this region so far as I am acquainted with it, points to a synclinal structure, or more accurately fan structure, between the Brahmapootra and the Yangtze, induced by a pressure acting from west to east as the final phase of crust movement, which breached a continuous Sino-Himalayan axis, the result of a previous crust movement from south to north. The present hydrography of the region is due to a fusion of two sets of rivers which have become involved since the second phase of crust movement; the peculiar loops into which some of the rivers have been thrown must be ascribed partly to the buckling and twisting of vertical strata consequent on pressure acting at right angles to the dip, whereby rivers following the strike of the rocks have been thrown out of their course. Finally, there has been a rift formation in addition, due to a lateral tension strain, acting at right angles to the long axes of the synclines, or to a sagging of the anticlines with consequent rupture of the synclines. Complications have been introduced by the bursting through of enormous masses of eranite, which have tossed aside and altered the sedimentary rocks. The whole of this region must once have been under water like the Hkamti plain, but in the east subsequent alteration has gone so far that there are no clays and sandstones left, and the further east one goes the greater is the metamorphism and crumpling of the rocks. Possibly the pressure which gave rise to these mountain ranges is still acting from the west, and the white mountains which lift up their heads so proudly will grow yet higher and grander; but the fires which blasted this corner of Asia are drawn, the great lakes are drained. Only the restless rivers still pour through the terrific breach in the Asiatic divide to the hot south, to be followed through the rent they had torn not less impetuously by the hordes of hardy northmen who, six centuries before Christ, overran the plains of Indo-China. NOTICES OF MEMOTRS. Arresian WarTeR 1N Manrropa.’ By J. B. Tyrrex. OR many years, in fact almost ever since Winnipeg has been a city, it has depended for its water supply on wells sunk through the impervious layer of Boulder-clay which underlies the city, into a bed of porous limestone from which water rises in great abundance. From these wells the city has been able to obtain 1 From the Canadian Engineer, vol. xxvi, No. 15, p. 574, April 9, 1914. 220 Reviews—The Coals of South Wales. a plentiful supply of water which, while containing a slight amount of mineral matter, is absolutely free from any hurtful bacteria, or from organic germs of any kind. The porous limestone into which these wells are sunk, and from which the water rises, extends to the north and west beneath a layer of Boulder-clay, and rises to the surface in a number of places in the country between Lakes Winnipeg and Manitoba at elevations varying from about fifty to one hundred and fifty feet above the level of the prairie at Winnipeg. The rain falls on these bare rocky areas, as well as on the adjoining clay-covered country, but instead of flowing away in rills and streams, as it does on the clay-covered country, it at once sinks into the porous limestone and flows through this limestone southward and eastward until it finally reaches the surface either in the large springs north of Winnipeg or through the wells at the city of Winnipeg itself. The quantity that flows from these springs and wells is therefore largely limited to the amount of the rainfall on those portions of the surface where the porous limestone is uncovered. Where it is covered, as it is in many places, most of the water derived from the rain either stands in small lakes and evaporates from the surface, or drains off towards Lake Winnipeg or Lake Manitoba by the many streams which unwater the country. The underlying porous limestone through which the water percolates on its way from the exposed areas north-west of Winnipeg to the wells in Winnipeg is a magnificent natural filter which is protected from contaminating influences throughout the populated parts of Manitoba by a thick covering of impervious Boulder-clay. No other city on the continent is provided by nature with such a filter, and no city could afford to duplicate it. RAV LEw Ss. horney I.—Memorrs oF THE Grotoeicat SurvEY oF ENeLAND and WALES. Tur Coats oF Sourn Wats, WITH SPECIAL REFERENCE TO ‘THE Origin and Disrripurion or AntHracireE. By AuBrey SrraHan, M.A., Sc.D., LL.D., F.R.S8., and W. Pottarp, M.A., D.Sc., F.1.C., assisted by E.G. Raptry. 2nded. 8vo; pp. 78, with 10 plates. 1915. Price ls. 6d. E. Stanford, Long Acre, or any agent for the sale of Ordnance Survey Maps. WITH A MAP, reproduced from Plate IV by permission of the Controller of H.M. Stationery Office.) NOR a long series of years the energies of those geologists who are also chemists seem to have been so concentrated upon questions of crystallization and the differentiation of igneous magmas that the corresponding and equally interesting problems of continuous variation in the composition of beds of sediment have remained outside the scope of their activities. To the nation sedimentary rocks are at least as important as igneous rocks. To our industries they are even of greater importance; and to those who have been called in to. help in mobilizing home resources of raw materials and providing manufacturers with efficient substitutes for sedimentary materials. till lately imported in bulk from abroad, the failure to take stock of _ this whole class of the nation’s resources has seemed a neglect which Reviews—The Coals of South Wales. 221 requires to be taken in hand at once. Among sedimentary rocks there is no class so essential to commerce as coal, and among coals there are none of greater national importance than are the anthracites of South Wales. It is therefore only to be expected that when we seek the best available account of the composition of beds of sediment and the lateral variation of those compositions from place to place, we should find it in a publication of H.M. Geological Survey which deals with the coals of South Wales. Ever since the days of De la Beche and Playfair (1848) the steam coal of the Navy has been a subject for chemical specification and research ; but though analyses of coals from many localities have accumulated, the geological data concerning the samples were generally so little precise that until the present century the results of the analyses have hardly been dealt with by geologists and do not seem ever to have been employed to throw light upon the natural history of the rocks. The Geological Survey Memoir on the Coals of South Wales was first published in 1908. Its main feature was the assembling of a great number of trustworthy and complete analyses of coals which had been collected, with proper precautions in sampling, from all the more important coal-seams, at localities which were distributed as widely as possible over the length, breadth, and thickness of the Coal-measures of the South Wales Coal-field. The analyses were all performed systematically, by standard methods, on samples collected by men whose business is not the buying or selling of the coal; and being all therefore strictly comparable with each other, they have proved of special value to those who are concerned with the commercial exploitation of the field. For the geologist, whose main concern is with the generalizations which emerge from the statistical treatment of these tabulated analyses, rather than with the figures themselves, it was the summarization of the analyses, each under the so-called “index of anthracitization”’ (a number obtained by dividing the percentage by weight of carbon by the percentage by weight of hydrogen contained in the coal), which marked the great advance. Until the memoir appeared, the view that, in South Wales, anthra- citization of the coals was an event contemporaneous with the deposition of the measures, was only one among several alternative hypotheses. Now, however, as the result of the field and laboratory work set forth in the memoir, this hypothesis has advanced to the foremost place, and the diagram maps, which show the iso-anthracitic lines for each of the more important seams or groups of seams over the coal-field, form an excellent demonstration of the forcefulness of the evidence which supports it. Iso-anthracitic lines are obtained by plotting, on separate maps for each coal-seam, the index of anthra- citization for the samples of coal analysed, each at the geographical locality from which it was collected, and by drawing contour-lines among the ‘ spot-levels’ so obtained. In each of the seams or groups of seams for which they are illustrated, the iso-anthracitic lines have come out as sweeping sub-parallel curves, which range about axes or centres peculiar each to the particular seam or group of seams which Reviews—The Coals of South Wales. 222 ‘aoO frau0eyg + ’ H jo OT[OIJUOD oq} jo uorssturted kg -(GT61) “po pug ‘apoviyjup fo uoynquysig pun wbruig ay) 07 a0uawafa.. yoroads yquM aA yynog fo sppop ay,j, WO Tome foams [eodofooy oxy ut poystqnd ‘det jvursti10 ayy wosy (poonpor Ayyeeas) peonpoadoy | ga 4333- 3NIN NI or Satiw ao A1v2G uabosphy a uaquDy Jo woryn/ae 94) Burmays 4aqumu ayy ‘saury 21y19D14jUD-OST Og, sashjouy x TA GAMINVLE HO oe Ias4-a4Niq sv]-sva 3 7] DILIOVEHINY-OS] ONIMSHS d1alLj-1V07) SSHIVM HLINOG upADIegy 2, ~“banly Reviews—The Coals of South Wales. 223 is the subject of the illustration, which centres are situate in some eases within, in others beyond, the present northern boundary of the coal-fieid. (See Map on p. 222.) Assembling the alternative hypotheses for the purpose of destructive criticism, Dr. Strahan notes that in taking the view ‘‘that the differences between anthracitic and bituminous coals in South Wales are mainly due to original differences of composition ’’? he was guided by four main considerations, the first three of which seem to be adequately proven by the diagrams given to show the distribution of iso-anthracitic lines. These four considerations may be summarized as follows: (1) ‘‘ Groups of seams possess a certain individuality,’’ and ‘‘in some there are local anthracitic areas of which no evidence appears in others . . . but bands of the same seam may show considerable differences of composition’. (2) ‘‘Iso-anthracitic lines show no definite connexion with the faults and disturbances,” and ‘‘ though the strata may be vertical or even inverted and sharply folded as in Gower, yet the coal-seams retain the composition proper to that part of the coal-field”. (3) ‘‘ Anthracitization is obviously not connected with the existing outlines of the coal-field as determined by denudation,” and ‘‘ there is no connexion between anthracitization and depth from the present surface”’.. (4) is based upon the con- sideration of the proportion of inorganic ash which remains when the coals are combusted. ‘‘The comparative freedom of anthracitic coals from ash” was ‘“‘ already brought out by Mushet’s analyses” as long ago as 1840, but it has remained for the present generation to discover that when a sufficient number of Welsh coal analyses are assembled the percentage of ash rises ‘‘ with fairly steady gradient from 1 per cent at the anthracitic end to more than 6 per cent near the bituminous end of the scale’’. These four main considerations all point to an early date for the formation of the anthracite of South Wales, and if it be accepted that variation in the percentage of ash ‘‘ cannot be due to subsequent alteration” of the coal it must follow that anthracitization took place contemporaneously with the deposition of the Coal-measures. A fifth line of evidence, based upon the finding of certain ‘‘ true pebbles” of coal (remanié from the breaking up of some already consolidated seam) among the sandstone pebbles which form the conglomeratic beds interstratified with the Pennant Grits of the Upper Middle Coal-measures, clinches the argument. In the second edition of the memoir now before us the number of tabulated analyses has been increased to 821, which, with the inclusion of the results of direct determinations of the percentage of moisture and of the calorific value for forty-seven of the samples analysed, will make it by so much the more valuable to commercial men. The new samples have been collected during the recent revision of the maps of the coal-field, all under the standard conditions of sampling observed for those dealt with in the first edition. Of the 118 new analyses, some were done in the Survey laboratory and many by the staff of the Government laboratory : much credit is also due to Mr. C. A. Seyler, who, working first for and later in collaboration with the officers of the Geological Survey, has 224 Reviews—Mineral Resources of Great Brita. been responsible for no less than 101 of the analyses now tabulated. So far as the geological conclusions are concerned, all the arguments put forward in the first edition are somewhat strengthened, and the net result of the revision is a greater precision in the location of the lines of iso-anthracitization in the charts for the various seams. In the letterpress we find additional comments by Dr. Pollard upon certain more modern methods of analysis introduced by American and other chemists since 1908, but for the sake of uniformity none of these has been adopted. In the last pages of the memoir Dr. Strahan allows himself to draw tentative conclusions concerning the physical geography in South Wales and Ireland in Carboniferous times, and we find it definitely suggested that it was some peculiarity of physical geography in South Wales and Ireland which led to the differentiation of the material in the coal-seams. ‘‘ As the coast-line retreated northward the area of anthracite coal shifted and kept pace with it,” and the rule ‘‘that each seam in any locality is less , anthracitic than its predecessors . . . is a necessary accompaniment of the formation of anthracite at successive intervals at a more or less constant distance from a retreating shore-line’’. Of the labour involved in the preparation of the memoir only those who have personal experience of quantitative analysis of coal are competent to judge. The general laws governing the ‘‘ oradation into anthracite’? in South Wales have been made clear, and even allowing for the unique opportunities offered by a coal-field which is in course of active development over almost the whole of its extent, it may be fairly claimed that this is no small accomplishment, a result certainly to be accounted as of ‘‘ both scientific and economic value’’. What has been done for anthracite may be extended to other groups of sedimentary rocks, and if geologists who have adequate experience of the arts of chemistry, or chemists who have sympathy with the requirements of geology, can be persuaded to take up the work, further discoveries of equal scientific interest and of perhaps even greater advantage to the nation’s commerce should reward their efforts. To such workers we commend the second edition of the Survey memoir on the Coals of South Wales as a model worth following when they present their results. W. G. F. IJ.—Tue Gronogican Survey on THE Mrnerat Resources oF Great Brrrary. ee the stress of a protracted war it behoves belligerent countries to’ take careful stock of their resources. The special reports by the Geological’ Survey on the Mineral Resources of Great Britain, of which three volumes have appeared—the first (pp. 59, 1s.) on Tungsten and Manganese Ores, the second (pp. 93, 1s. 6d.) on Barytes and Witherite, and the third (pp. 57, 1s.) on Gypsum and Anhydrite—are timely and very welcome. Some legitimate surprise may perhaps be felt that such obviously useful publications had not been issued long ago, before the cloud of war loomed and broke, but in this country the State was ever chary of assisting and stimulating industry, and the Geological Survey constitutes no exception to the general rule of Government departments. It is remarkable that for Reviews—Lower Paleozoic Fossils of Burma. 225 many substances of vital importance either for or in connexion with the production of munitions of war we should have allowed ourselves to be entirely dependent on foreign sources. Tungsten is a case in - point. Practically all the ore is produced in the British Empire, yet it was all shipped to Germany and worked up there. The country is, however, now awake to the danger of allowing key industries to be entirely in hands which might become hostile. Another urgent reason for making the most of resources actually in the country is the necessity for restricting our imports as much as possible. Intelligent prospecting might bring to light mineral ores from which might be produced many chemical substances at present imported and fast growing scarce. All the volumes follow very similar lines. The chemical composi- tion and physical properties of the minerals supplying the substances in question are described very briefly; this section might with advantage have been expanded so as to make the identification of the minerals easier for those not skilled in the subject. A section follows on the commercial uses, with statistics, and the method of treatment. The mode of occurrence is then discussed, and -the principal mines are described in some detail. The list of localities is not exhaustive: possibly none were included which were not repre- sented by specimens in the Museum in Jermyn Street. Of the substances dealt with, tungsten and manganese are largely used for alloying steel, the former having also an extensive use for the filaments of incandescent electric lamps; barytes is required in the preparation of white paints and for wall-papers, while witherite is the principal source of barium compounds; gypsum furnishes the familiar plaster of paris, and celestine and strontianite are the sources of the strontium used in sugar refining. Il1.—Lowerr Patmozorc Fosstts or Burma. SuerpLeMENTARY Mermork on NEW OrDovicIaAN AND Siturran Fossixs FRoM THE NortHEerN Swan States. By F. R. Cowper Reep. Paleontologia Indica, n.s., vol. vi, Mem. 1, viii + 98 pp., 12 pls., 1915. (Y\HE memoir to which this is supplementary was published in December, 1906, under the title The Lower Palgozoice Fossils of the Northern Shan States, Burma, by F. R. C. Reed, with a Section on Ordovician Cystidea, by F. A. Bather. In that memoir fossils were described from the Naungkangyi and Nyaungbau Beds of the Ordovician, and from the Namhsim and Zebingyi Beds of the Silurian. From those beds further fossils are now described, but the chief interest lies in those from two fresh sets of beds which are, on their evidence, referred to Lower Silurian and Middle Ordovician. _ The stratigraphical succession, from above downwards, is as follows. Sizurran: Zebingyi Stage, transitional to Devonian ; Namhsim Stage, consisting of the Upper or Kénghsa Marls, with Phacops shanensis, correlated with Lower Ludlow, and the Lower or Namhsim Sandstones, with Phacops longicaudatus, var. orrentalis and Lllenus namhsimensis, n.sp., correlated with Wenlockian; and the DECADE VI.—VOL. III.—NO. V. 15 226 Reviews—Lower Palwozoic Fossils of Burma. Panghsa-pye Stage, consisting of an Upper or Graptolite Band and a Lower or Trilobite Band (to these we shall recur). Onpovicran : Nyaungbaw Limestones with ‘‘Camarocrinus asiaticus” ; the Upper Naungkangyi Beds, comprising the Hwe Maung Purple Shales; the Lower Naungkangyi Beds, with the rich Cystid fauna of Sedaw, probably Llandeilian ; and the Ngwetaung Sandstones with a species of Orthis. The rocks of the new Panghsa-pye Stage are of interest, not merely from their richness in organic remains, but from the occurrence of graptolites in the upper beds. These, as determined by Dr. Gertrude Elles, indicate three horizons, two of Lower Llandovery age, and the third suggestive of the Wenlock Shale. From the lower Trilobite Band are recorded some plates assigned to Zurrilepas, but, since no figures are given, it is impossible to decide whether this reference would be correct according to more recent views. The Upper Naungkangyi Beds, of which the Purple Shales may be a local facies, are exceedingly fossiliferous and have yielded many new species. The trilobites on the whole indicate an horizon corresponding with Stage C of the Baltic Provinces, and Ashgillian types do not appear. In both sets of beds there occurs a new lamellibranch of the Family Vlastide, which Dr. Reed names Shanina vlastoides. The trilobite Pliomera ingsangensis Reed, has also been found in both facies, and is now made the type of a new subgenus Lncrinurella. Of this subgenus no definite diagnosis is given, but the main diagnostic characters appear to reside in the glabella, which resembles that of Hnerinurus. On p. 97 Dr. Reed notices ‘‘the absence of cystideans”’ from the Hwe Maung Purple Shales; but Mr. T. H. D. La Touche, to whom the distinction of these beds is due, said: ‘‘ the more argillaceous portions of the rock are highly fossiliferous, containing large casts of fragments of crinoid stems, cystidean plates, etc.” (Mem. Geol. Surv. India, xxxix, part 2, p. 92, 1913). Reference to Mr. La Touche reminds us that in the same paper (p. 65) he stated definitely, what those familiar with the literature had already assumed, namely that Camarocrinus asvaticus Reed, was identical with Lchinospherites kingi Noetling (see Guot. Mae., 1892, p- 521). The reference of Camarocrinus to Scyphocrinus was also made clear at least as early as 1907. From this it would appear that Camarocrinus asiaticus should be known as Seyphocrinus kingt. It is, however, very doubtful whether Noetling’s name can be accepted, so that we may perhaps correctly speak of Scyphocrinus asiaticus. Dr. Cowper Reed is to be congratulated on the enthusiastic industry with which he tackles these large and varied collections of fossils. ‘The same congratulations can hardly be extended to his would-be readers. It may be that, in the present case, the War has increased the natural difficulty of correcting proofs from a printer in Caleutta; but mis- spellings and misplaced commas are minor evils. What is to be deprecated seriously is the impression conveyed by so many of these large memoirs, that they are notes jotted down currente calamo and sent to the press without further revision. From too many sentences the author’s meaning can only be extracted by a prolonged process of 0 Reviews—Dutch Pliocene Fauna and Flora. 227 interpretation. Till Dr. Reed shows more respect for his public, his erudition, energy, and ability will not receive the recognition that is their due. 1V.—Tae Puriocene Froras or tran Dorcu—Prusstan Borper. By Crirment Rep, F.R.S., and Exeanor M. Rem, B.Sc. Mededeelingen van de Rijksopsporing van Delfstoffen, No. 6. pp. 180, with 4 text-figures and 20 photographic plates. ’s Gravenhage: M. Nijhoff. 1915. Price fr. 16.50. R. AND MRS. REID have developed on lines of their own the study of the fossil fruits and seeds of the Tertiary floras. They have worked for many years on the Pleistocene and Pliocene deposits ot Britain ‘‘in the hope of obtaining some approximate measure of geological time, some idea of the succession of climatic changes, and some insight into the origins and migrations of successive faunas and floras”. Asa result of their work we have become acquainted with a sequence of small floras working backwards from the comparatively modern Roman deposits through Celtic, Neolithic, Glacial, Inter- glacial, and early Glacial strata to the latest Pliocene stage repre- sented in the Cromer Forest-bed. But as in Britain there is here a break in the succession, the earlier Pliocene deposits being marine and containing no plants, the authors have been forced to look abroad for the continuation of the history of the Pliocene flora of North- Western Europe, and hence have undertaken the examination of the Phocene flora which has been recently discovered at Limburg on the Dutch—Prussian border. In view of the remarkable results obtained from the study of the Upper Plocene flora of Tegelen, which were published in 1907, the publication of the detailed account of Mr. and Mrs. Reid’s further work in the same region has been awaited with much interest. ‘The Reuverian flora, as the authors style it, from the name of the principal locality, is found to be of an older type than the Tegelian, ' though many plants are common to the two. It indicates a warmer climate, and is classed as Middle Pliocene. Up to the present nearly 300 species have been examined; of these the authors have been able to suggest the botanical position of about 230 ‘‘ with some degree of certainty’, and of a lesser number ‘‘ with considerable certainty.’’. The results arrived at are of great interest. ‘The trees and shrubs, which form the most peculiar and striking element in the flora, show a close relationship with the mountain flora of Western China at the ‘present day. Thus, among the species found in Limburg are Gnetum scandens, Magnolia Kobus, Zelkowa Keakt, and other present-day Chinese species. Others occur which, belonging to genera now extinct in Kurope, are still represented in China by closely allied species; such is Meliosma europea, closely allied to IL, Veitchiorum of the mountains between China and Tibet. Again, when the genus in question is common to both Europe and China, it is often a Chinese or Japanese species that most resembles the Reuverian plant. The Reuverian flora suggests a mean temperature similar. to that of Southern France to-day, but the Chinese alliance is more strongly 228 Reviews—Geology of Western Australia. marked than that with the existing flora of the Mediterranean area. The flora as a whole was probably much richer in species than the present-day Central European flora, and was possibly comparable in variety, in the number of its species, and in the abundance of its trees and shrubs with the present-day flora of Western China. Coming to general considerations of plant-distribution, the authors, developing the now well-known resemblance between the Eastern North American and East Asiatic floras, conclude that the Reuverian fossils indicate one of three great streams of migration southwards from a common centre in the north, the other two being the Chinese and North American. The two latter found an open route to warmer regions and survived; the Reuverian, on the other hand, found a barrier of seas, deserts, and mountains and perished under the rigorous climatic conditions before which it was retreating. The greater part of the volume is occupied with a detailed systematic description of the fruits and seeds which have been separated from the lignitic material. Some botanists may find points of issue with Mr. and Mrs. Reid in their general conclusions or in some of their specific determinations, but all must admire the wonderful patience, industry, and skill of which the present work is a monument. The hundreds of beautiful photographic reproductions of the objects described are alone of inestimable value. We hope that the authors will be able to continue their exploration of these interesting deposits. AC Beans. V.—GerotocicaL SurvEY oF WerstERN AUSTRALIA. ULLETIN No. 61, An Outline of the Phystographical Geology (Phystography) of Western Australia, by J. T. Jutson, is a deliberately educational volume designed to aid the citizens of the State to a juster appreciation and a greater knowledge of the land in which they dwell. The treatment throughout is thoroughly modern, and owes much to the American school of geographers headed by W. M. Davis. West Australia is a country of extreme geological antiquity, and its great interior plateau, formerly a peneplane, is now in a cycle of desert erosion. It presents a series of unique physiographical problems, of which, notwithstanding the present work, only the fringes have been touched. Mr. Jutson has produced a work of extreme interest, readable throughout, which will certainly form the starting-point for all future investigation of this subject in Western Australia. Bulletin No. 56, Zhe Geology of the Country between Kalgoorlie and Coolgardie, by C.S. Honman, serves as a connecting lnk between previous bulletins describing the country around the above-mentioned mining centres. The rocks consist of a series of inclined and folded metamorphosed sedimentary rocks, probably Pre-Cambrian in age, with intercalated beds regarded as volcanic rocks. The whole series is invaded by basic and acid intrusive rocks, but, unlike the neighbouring areas, it contains few ore-deposits. The scale on which geological surveys are carried out in our great Dominions — ti . | | Reviews—Professor Bonney—On certain Channels. 229 is exemplified in Bulletin 57, A Geological Reconnaissance of a portion of the Murchison Goldfield, by H. P. Woodward. We are told that the area dealt with embraced 3,300 square miles, and that the work was carried out chiefly in 1912 with some unavoidable interruption. The country consists chiefly of granite, with ancient crystalline schists, and shows wonderful examples of arid erosion, many of which are figured. The bulletin contains an account of the economic geology of the area, including two tin fields, an occurrence of emeralds, and aboriginal ochre mining. The emeralds are derived from pegmatite veins cutting mica-schists, and the occurrence is of value as the gem is now very scarce. Bulletin No. 59 is a collection of Miscellaneous Reports containing eighteen short papers, mostly preliminary observations on various ore-bearing areas of the State, issued in this form so as to ensure prompt publication of the valuable mining information they contain. Gold is, of course, the main quest; but occurrences of tin, lead, copper, coal, and rare metals are also dealt with in this bulletin. There are also two petrological papers, and one on Western Australian meteorites. Cowan: VI.—Ow cerrain CHANNELS ATTRIBUTED 10 OVERFLOW STREAMS FROM Icz-pammep Laxrs. By Professor T. G. Bonnny, F.R.S. pp. 44. Cambridge: Bowes & Bowes. 1915. Price 1s. LTHOUGH Professor Kendall’s explanation of the so-called overflow channels of the Cleveland district has been applied to similar phenomena in East Lothian, Cumberland, Dublin, and elsewhere, a number of objections of a general character have been raised from time to time. In the Presidential Address to the British Association in 1910 Professor Bonney stated the difficulties involved in the “‘land-ice theory’, and in the pamphlet under review these difficulties are reiterated and the result of a detailed examination of several of the above-mentioned localities discussed. Although at the present day marginal lakes are uncommon, most of the Alpine examples being small and possessing no overflow channels, certain criteria such as beaches, deltas, floor-deposits, and overflow channels are considered to be indicative of the former presence of such lakes. In the case of Glen Roy the evidence consists mainly of the first two, but in the North of England the last is the only significant criterion. Professor Bonney holds that the ‘railway cutting’ trenches must have been cut by mature rivers, and that their form is not such as would be expected from lake overflows, even where the latter would carry much debris. He prefers to consider them as the ‘‘ relics of ancient, sometimes very ancient, valley systems and not such modern features as the glacial theory demands”. Various facts seem to favour this hypothesis: for example, the channels sometimes occur in an aligned series, while they are often cut by later transverse streams. Again, overflows would tend to be spasmodic, while the resultant trenches would, like Alpine sub-glacial streams, tend to be V-shaped. The absence of deltas seems significant, since overflow streams would 230 Reviews—Ore Deposits, Alaska Peninsula. be heavily charged with debris; Thoroddsen has recently described the blocking-up of fiords in Iceland by the debris carried by jokull-vatn. The glacial theory of the in-and-out channels is also unsatisfactory. In the case of a stream flowing between a glacier and a hillside it is very probable that the latter would be much more resistant than the former, so that the stream would tend to cut its way into the ice and to lower the level of its bed. Thus, instead of a flat ‘bench’ along the hillside, the latter would be in the form of a shelving slope working gradually towards lower ground. Professor Bonney offers two alternative explanations: one that the ‘out’ portions are the remnants of. valleys, one wall of which has been worn away by marine erosion ; the other, that one bank has been greatly steepened by warping subsequent to the formation of the channels. The widespread occurrence of these dry valleys and the variety in form render it probable that no single explanation satisfies all the examples. Some must be assumed, at present, to be due to ‘overflows’, as it is impossible to correlate them with any former drainage systems; others, such as the large cross-cut near Cader Idris, strongly favour the view that such channels may originate without the assistance of glacier lakes. It also seems possible that some may arise by the re-excavation or clearing out of older filled-up valleys by the action of glacial streams. This would explain why these pre-glacial valleys are free of glacial material and at the same time satisfy the glacialists who maintain that the form of the trenches is that which would be expected from the action of heavily laden streams with comparatively low gradients. A. 8S. VII.—Gerotogy anp Ore Depostrs or Copprr Mountain anp Kasaan Prninsora, Atasxa. By C. W. Wricur. U.S. Geol. Sury. Prof. Paper No. 87, 1915. pp. 110, with 22 maps and plates. ({\HE Prince of Wales Island, the largest of the southern islands of Alaska, is separated from the mainland by Clarence Strait, which with its numerous branches breaks South-Eastern Alaska. into numerous islands and peninsulas. The network of fiords extends northward from the Portland Canal. The country shows abundant signs of glaciation, but has no existing glaciers, and owing to its mild moist climate, its latitude of only 55° to 56°, and its long summer days, it is covered with a vegetation which, though mainly coniferous, is often as dense as tropical jungle. These forests have greatly hampered the geological survey of the area, which has been stimulated by its valuable copper deposits. The survey by Messrs. F. E. and C. W. Wright shows that the country has an Archean foundation, on which rest Silurian, Devonian, and Carboniferous sediments. During Lower Mesozoic times it was intruded by a great series of plutonic rocks, and extensive andesitic lavas were discharged on the surface. As usual in Alaska, the chief Kainozoic formation is a great series of continental sediments of Eocene age; they were followed by basaltic eruptions, some of which have taken place in post-Glacial times. ' a ’ — ” ——— ee Reviews—Tertiary Mollusca, New Zealand. 231 The complex of fiord channels and valleys is shown by the geological maps, especially by that of the Kasaan Peninsula, to be quite independent of the older grain of the country; the arrangement of the fiords is inexplicable on any theory of glacial erosion, and is only explicable by their origin along intersecting Upper Kainozoic fractures. The ore deposits are numerous bodies of copper ores in the contact zone, where granite has been intruded into limestones. The - ores occur in shoots, which though near the contact are not exactly along it. ‘The memoir is a valuable addition to the economic geology of Alaska. VIII.—Revision or tar Tertiary Motiusca or New ZrALaND, BASED on Type Marertat. By H. Sorer. New Zealand Geol. Surv. Pal. Bul. No. 3, pt. ii, 1915. pp. vii, 69, with 9 plates. \ R. HENRY SUTER, the consulting paleontologist to the il Geological Survey of New Zealand, has completed his useful redescription of a series of types of New Zealand Kainozoic Mollusca of species founded by Hutton, Mr. EK. de C. Clarke, Dr. J. A. Thomson, and Professor Marshall. He has established one of McCoy’s list Names as a new sub-species. ‘The revision is illustrated by nine excellent plates. The species range from the Miocene to the Pleistocene; the majority are Pliocene. Mr. Suter accepts the Oamaru Beds as Miocene, which is consistent with the conclusicns of McCoy and Chapman as to the age of the corresponding fauna in South-Eastern Australia. On p. 37 he, however, leaves the Australian range of Bathytoma haasti as Kocene, whereas from the localities cited it would also be more correctly included in the Miocene. IX.—Tue Inorcanic Constituents or Ecarnoperms: By F. W. Crarke and W. C. Wueeter. U.S. Geol. Surv. Prof. Paper No. 90L, 1915, pp. 191-6. ESSRS. CLARKE AND WHEELER have extended their interesting researches on the composition of the Crinoid skeleton to the KEchinoids and Stelleroids. ‘hey find by nine analyses of Echinoid plates that the amount of carbonate of magnesium in the shell ranges from 6 to 134 per cent, and that the geographical distribution of the specimens shows that the proportion of magnesia is inversely to the latitude. A series of analyses of the joints of the Starfish and Ophiuroids shows the same conclusion ; the proportion of magnesium carbonate ranges from 7:79 to over 14 per cent, and as a rule the proportion is highest in specimens from the warmest seas. A limestone therefore formed of the remains of Echinoderms which had grown in a warm sea would give rise to a magnesian limestone. The authors announce their intention of extending their investigation to other marine invertebrates to determine whether their skeletons show the same distribution of magnesia, so that magnesium sediments would naturally be deposited more in warm than in cold climates. 232 | Brief Notices. X.—Brier Norticrs. 1. East Loruran. By T.S. Murr. Cambridge County Handbooks. pp. 177. 1915. Price 1s. 6d. net. ; HIS useful little volume maintains the high standard of the now familiar series to which it belongs. The county includes parts of the Central Plain and of the Southern Uplands, and boasts a picturesque coast, thus affording scope for a highly interesting geographical study. 2. Vicror1an Tritopites.—In his series ‘‘ New or little-known Victorian Fossils in the National Museum”, Mr. F. Chapman has recently published a description of some Trilobites from the Yeringian (Upper Silurian) beds. These include new species of Goldius, Cyphaspis, and Calymene. Other genera represented are Proétus, Cheirurus, and Phacops. In adopting De Koninck’s name Goldius, 1841, in place of Goldfuss’ Bronteus, 1843 [not 1834], Mr. Chapman might have given a reference to the original publication. Life-size photographs of the specimens are reproduced, and when these fail in clearness an enlarged drawing is added—a very good plan. 3. HQuimseTITES IN JuRAssIc SHALE, WontHacel, Vicrorra.— Under the name Lguisetites wonthaggiensis Mr. F. Chapman describes the tuberous underground shoot of an equisetalean found in Jurassic shale from a boring at Wonthaggi, Victoria. Though Zquisetites has previously been described from South Gippsland, this is the first record of this particular structure from Australia (Rec. Geol. Surv. Victoria, vol. ili, p. 317). 4. Tue Ort anp Gas Fretps or Onrarto aND QueEBec. By Wryarr Matcoum. Canada, Department of Mines, Geological Survey, Memoir 81, No. 67 Geological Series, Ottawa, 1915. pp.i11+248. N this memoir the author sets forth concisely the geological conditions existing in the southern parts of Ontario and Quebec underlain by sediments which have suffered little disturbance. The most important oil- and gas-producing fields lie in South-Western Ontario. The oil pools of Oil Springs and Petrolia, opened fifty years ago, occur in the Onondaga (Coniferous) formation, but gas and oil have been found in the Salina (Onondaga), Guelph, Clinton, and Medina formations. There has recently been a rapid decline in the production of oil in spite of the discovery of new pools, but the gas production has increased rapidly. 5. Coat Fretps anp Coat Resources or Canapa. By D. B. Dowxine. Canada, Department of Mines, Geological Survey, Memoir 59, No. 55 Geological Series. pp. vili+174. Ottawa, 1915. fJ\HIS memoir is reprinted with some additions from the report on the Coal Resources of the World presented to the Twelfth International Geological Congress. Canada appears to have large reserves of coal, but much of it is not available for the commerce of the British Empire. Large supplies of bituminous and sub-bituminous coals exist in the western interior, and to a lesser extent on both i D . | | ee ee ae Brief Notices. 233 coasts. The fields in Manitoba and Southern Saskatchewan supply lignitic coal well adapted for domestic use. The extensive coal- fields of Alberta, containing coals of a wide range of character, form Canada’s greatest coal reserve. The interior of British Columbia contains many coal areas. 6. Tue Position oF THE VIBRATION PLANE OF THE PoLARISER IN THE PxrrograpHic Microscopr. By F. E. Wricar. Journ. Washing- ton Acad. Sci., v, pp. 641-4, 1915. N petrographic microscopes with fixed polarizers the plane of the transmitted light is parallel to either the vertical or the horizontal spider-line of the eye-piece. The better position is that in which most light is transmitted. The light from the sky is always partially polarized, the amount varying with the distance from the sun’s position, and further effect is produced by the reflection at the sub- stage mirror. ‘he second factor was found to be negligible. The first, however, is important, and to obtain the best illumination the observer should set the plane of the polarizer parallel to the vertical spider-line in the early morning and late afternoon, and at right angles thereto at midday, but, since the intensity at midday is so much greater than when the sun is low, the better position for a fixed polarizer is for the plane to be parallel to the vertical spider-line of the eye-piece. 7. A Surprz Device ror tat GrapuicaL SoLvrion oF THE Equation A=8.C: a Guotoeicat Prorracror. By F. E. Wricur. Journ. Washington Acad. Sci., vi, pp. 1-7, 1916. Y the use of reciprocals the variables may always be taken as less than unity. Rectangular co-ordinates, together with an arm revolving about the origin, are used in conjunction with squared paper, the scales being varied to suit the particular equation. The geological protractor is a particular form: from it the apparent dip of a bed can be read off directly for any angle of dip of stratum and for any azimuth of vertical section. 8. THe CorreLation oF Porasstum AnD Maenestum, Soprum anv Iron, In lenxous Rocks. By Henry S. Wasnineton. Proc. Nat. Acad. Sci., i, pp. 574-8, 1915. fJVHE correlation of the elements has not yet received much study except the relation based upon silicity. It appears that in igneous magmas potassium and magnesium, and sodium and iron, tend to vary together, the evidence being of two kinds—petrological and mineralogical. 9. PREssuRE as A Factor in THE Formation oF Rocks anp MINERALS. By Joun Jounstoy. Journal of Geology, xxiii, pp. 730-47, 1915. ENERALLY the so-called physical changes (e.g. the melting- point of a pure substance) has been overestimated as compared with the influence of pressure on chemical changes. Change of effective pressure will in general alter the configuration of the various fields of stability in a system, but the effect will not be marked unless the concentration of one of the components changes appreciably with the change of pressure. In any discussion of the 234 Reports & Proceedings—Geological Society of London. course of crystallization from a complex magmatic system the mode in which the effective pressure varies must be considered as well as the mode of cooling, for change of pressure may affect the order of erystallization. REPORTS AND PROCHEHDINGS. I.—Grotocicat Socrery or Lonpon. 1. February 23, 1916.—Dr. Alfred Harker, F.R.S., President, in the Chair. The following communication was read :— ‘‘On the Origin of some River-Gorges in Cornwall and Devon.” By Henry Dewey, F.G.S. (Communicated by permission of the Director of H.M. Geological Survey.) In North Cornwall, near Tintagel, there is an area of peculiar topography characterized by the presence of an upland plain or plateau. The plateau is dissected by deep gorges, with their walls scarred by potholes through which the rivers flow in a series of waterfalls, cascades, and rapids. aux This plateau is terminated inland by degraded cliffs rising abruptly from 400 feet above sea-level, while the plain slopes gently to the recent sea-cliffs, mostly over 300 feet high. The plateau has been cut across rocks of different degrees of hardness, and is overlain by deposits of detritus and peat. Wherever the plain occurs the scenery is featureless, and the land boggy and waterlogged. The widespread occurrence of this plain over Cornwall and Devon at a uniform height suggests that in its final stages it was a plain of marine erosion. ‘he author accepts Mr. Clement Reid’s conclusion that its date is not later than Pliocene. Its uplift in post-Plocene times led to rejuvenescence of the rivers, initiation of coastal cascades, and the production of gorges aided by the formation of potholes. At Lydford, on the western flank of Dartmoor, the uplift led to the diversion of the Lyd by a stream that breached the valley-side and tapped the head-waters of the river. A small stream, the Burn, now flows past Was Tor and Brentor, through the valley formerly occupied by the Lyd. The shortened journey to the lowlands bestowed such enhanced cutting-power upon the river that it quickly incised a chasm through which it now flows more than 200 feet below the base of its former valley; while a tributary enters as a waterfall from a hanging valley near Lydford Junction. The elevation of the land also led to formation of gorges of similar character in other upland plateaux. These plateaux have been described by Mr. Barrow in the Quarterly Journal of the Geological Society, and reference is made to them by the author in connexion with the effects upon them of the uplift. There are thus in Cornwall and Devon two characteristic types of scenery, to which in great part these counties owe their charm. Wide featureless plains covered with heath and marshland and dominated by tors and crags, on which the drainage is sluggish and vague, a Reports & Proceedings—Geological Society of London. 235 alternate with deeply incised rocky ravines where rivers flow as rapids and cascades. These two types mark successive periods of erosion. Post-Pliocene uplift gave such increased cutting-power to the rivers that they quickly incised chasms in their former valleys, employing while so doing the activity of waterfalls and rapids. 2. March 8,1916.—Dr. Alfred Harker, F.R.S., President, in the Chair. The President referred with regret to the death, on March 3, of Professor John Wesley Judd, C.B., LL.D., F.R.S., Past President of the Society. He spoke of the value of Professor Judd’s contributions to geological science, and of his eminence as a teacher of the science, and stated that the Society was well represented at the funeral. Dr. Aubrey Strahan, F.R.S., Director of H.M. Geological Survey, exhibited and described briefly a set of specimens from the Western Front, illustrating the character of the rocks in which trenches, tunnels, etce., are being dug. They included specimens from the Cretaceous and Tertiary formations showing remarkable similarity in characters to the contemporaneous formations in Britain. The following communication was read :— ‘¢ Fossil Insects‘ from the British Coal-measures.’”” By Herbert Bolton, M.Sc., F.R.S.E., F.G.S., Reader in Paleontology in the University of Bristol. The author describes six insect wings found in the Coal-measures of Northumberland, Lancashire, and South Wales. Three of these have been previously named, but not described in detail; the remaining three are new to science. Atdwophasina anglica, Scudder, has been examined in detail, and is now regarded as a primitive type of the Proto- Orthoptera, in contradistinction to Scudder’s view that it is a Protophasmid, and to that of Handlirsch, who had removed it to a group of unplaced Paleeodictyoptera. Paleodictyopteron higginsi is shown to be related to the Dictyoneuride. A new genus and species is created for, a finely preserved Wing, intermediate in character between the Dictyoneura and Lnthomantis. Among the varied fauna obtained from ironstone nodules in the Middle Coal-measures at Sparth Bottoms, Rochdale (Lancashire), is a basal fragment of a wing recognized as a new species of Sprlaptera, and this is now described. An unusual type of wing from the Northumberland Coal-field is very suggestive of the Protodonata, and is described as a KID a tive of a new genus and species. The author. also discusses the Proto-Orthopterous affinities of Pseudofouquea cambrensis (Allen). 236 Reports & Proceedings—Geological Society of London. — 3. March 22, 1916.—Dr. Alfred Harker, F.R.S., President, in the Chair. Dr. A. Smith Woodward, F.R.S., V.P.G.8., exhibited specimens of the problematical ichthyolite, Celorhynchus, trom an Eocene deposit in the Ombialla district, Southern Nigeria, and discussed the nature of this fossil. Microscope sections of the well-preserved Nigerian specimens confirmed W. C. Williamson’s determination that Celo- rhynchus is an essentially dermal structure. A similar section of part of the rostrum of the teleostean fish Blochius, from the Upper Kocene of Monte Bolea, near Verona, showed an almost identical structure. The precise nature of this rostrum remained to be deter- mined, but there could be no doubt that the so-called Celorhynehus is the corresponding part either of Blochius or of an allied genus. The following communication was read :-— ‘‘The Pseudo-Tachylyte of Parijs (Orange Free State) and its Relation to ‘ Trap-Shotten Gneiss’ and ‘Flinty Crush-Rock’.” By S. James Shand, D.Sc., F.G.S., Professor of Geology in the Victoria College, Stellenbosch (S.A.). The rocks which are here described as ‘ pseudo-tachylyte’ occur in irregular veins in the granite-gneiss of Parijs (O.F.S.) ; they formed the subject of a communication to the Society on November 18, 1914, which has since been withdrawn. The author first regarded them as igneous intrusions ; in the account now presented he compares and contrasts these rocks with the ‘ trap-shotten gneiss’ of India and with ‘flinty crush-rocks’ from Scotland, Argentina, and Namaqualand. The veins are utterly irregular in form, dip, and strike; they freel branch and anastomose, but not uncommonly terminate blindly. The material consists of a very dense black base, holding numerous rounded and subangular fragments of granite; these are sometimes so numerous that the base is reduced to the role of a mere cement between the rounded boulders. With regard to their microscopic characters, the rocks fall into three types, one of which is very opaque and almost without individualized grains or crystals, while the others represent different stages of crystallization of the first type. It is shown that the production of the veins involved a temperature sufficient to melt the felspar of the granite, and that there has been extensive recrystallization of felspar in the form of spherulites and microlites, and also of prisms of hornblende. In this evidence of very high temperature, and in the entire absence of shearing phenomena in the granite, the pseudo-tachylyte of Parijs ditfers from all known crush-rocks and has affinities rather with pitchstones and tachylytes. Among the crush-rocks of Scotland, however, the author (following Clough, Maufe, and Bailey) recognizes a passage from the clearly mylonitic type to a type in which fusion has been practically realized; the latter material is closely similar to the first of the Parijs types. A chemical analysis of the psendo- tachylyte shows that the total composition is practically that of a granodiorite, and is such as might correspond to an average of the very variable dark gneiss in which the veins occur. It is suggested that a ‘melt’ of granite, produced by mechanically developed heat arising from the sudden rupture of the granite, would Reports & Proceedings—Geological Society of London. 237 differ in certain respects from a normal magma of granitic composition, and it is thought most likely that the veins represent the solid equivalents of such a melt. 4. April 5, 1916.—Dr. Alfred Harker, F.R.S., President, in the Chair. The President announced that the Council had awarded the proceeds of the Daniel Pidgeon Fund for the present year to John Kaye Charlesworth, M.Sc., Ph.D., F.G.8., who proposes to conduct researches in connexion with the Glaciation of Donegal. The following communication was read :— “The Picrite-Teschenite Sill of Lugar (Ayrshire) and its Differ- entiation.””. By George Walter Tyrrell, A.R.C.Sc., F.G.S. This sill occurs near the village of Lugar in East Central Ayrshire, and is magnificently exposed in the gorges of the Bellow and Glenmuir Waters, just above the confluence of these streams to form the Lugar Water. It has a thickness estimated at 140 feet, and is intrusive into sandstones of the ‘ Millstone Grit’. The contacts consist of a curiousiy streaked and contorted basaltic rock, passing at both margins into teschenite. The upper teschenite, however, becomes richer in analcite downwards, and ends abruptly at a sharp junction with fine-grained theralite. The lower teschenite becomes somewhat richer in olivine upwards, but passes rapidly into horn- blende-peridotite. The central unit of the sill is a graded mass beginning with theralite at the top and passing gradually into picrite, and finally peridotite, by gradual enrichment in olivine and elimination of felspar, nepheline, and analcite. The field detail of the Bellow, Glenmuir, and other sections is given in part ii of the paper; and the petrographic detail, with several chemical analyses, in part ii. A unique rock, named lugarite in 1912, with 50 per cent of analcite and nepheline, occurs as an intrusion into the heart of the ultrabasic mass of the sill. Part iv deais with the special significance of this sill in petrogenetic theory. The mineral and chemical variations are described and illustrated by diagrams. It is shown that the average rock of the sill, obtained by weighing the analyses of the various components according to their bulk, is much more basic than the rock now forming the contacts. Hence, assuming that the sill is a unit and represents a single act of intrusion, the main differentiation cannot have occurred in situ. Other special features of the sill are the identity and banding of the contact rocks, its asymmetry, the density stratification of the central ultrabasic mass, and the sharp junction between the upper teschenite and the underlying theralite. The theory is advanced: that the differentiation units were produced by the process of liquation, but that their arrangement within the sill took place under the influence of gravity. There are sharp interior junctions between a unit consisting mainly of calcic ferro- magnesian silicates and a unit consisting mainly of alkali-alumina silicates with water, the former giving rise to the central ultrabasic stratum and the latter to the teschenites. These partly immiscible 238 Reports & Proceedings—Minerulogical Society. fractions arranged themselves according to density. Then within the central ultrabasic stratum there was a subsidiary gravity stratification—due to the subsidence of olivine crystals, giving rise to the graded mass described above. If differentiation had occurred subsequent to the arrival of the sill in the position that it now occupies, the contact rocks should have the same composition as the average rock of the sill. his, however, is not the case, as the average rock has the composition of an almost ultrabasic theralite, entirely different from the teschenites of the contacts. Hence it is believed that, after forming contact-sheaths of theralite, and under- going gravity stratification subject to liquation, the intrusion activity was renewed, and the sill was moved on along bedding-planes into cold-rocks, leaving its contact-sheath behind adhering to the old | contacts, and establishing new contacts with its upper and lower teschenite-layers. Here crystallization began, and, by the subsidence of olivine, the subsidiary gravity stratification of the central ultra- basic layer was effected. ‘The extraordinary flow-banding shown by the contact rocks affords confirmation of the renewed movement thus postulated. . In conclusion, the sill is compared with five other teschenite- picrite sills in Scotland, those of Ardrossan, Saltcoats, Blackburn, Barnton, and Inchcolm. II].—MuvyeratocicaL Socrery. March 21, 1916.—W. Barlow, F.R.S., President, in the Chair, Dr. J. W. Evans: A new Microscope Accessory for use in the determination of the Refractive Indices of Minerals. The accessory— a diaphragm with narrow slit adjustable in width—when placed in the primary focus of the objective or any point conjugate with it, serves several useful purposes. If placed parallel to the boundary between the two substances whose refractive indices are to be compared by the Becke method, it gives better results than an iris diaphragm. In the case of doubly refractive sections or grains in which an axis of optical symmetry lies at right angles to the microscope axis, the slit is placed parallel to the former axis, so that the paths of all the rays of light traversing it lie in a plane of optical symmetry and one direction of vibration is always parallel to the axis of optical symmetry, and a nicol is inserted so that the direction of vibration of the rays traversing it is parallel to the same axis: then the refractive indices of light vibrating parallel to that axis of optical symmetry may be investigated by the usual methods without the confusion caused by the bifocal images described by Sorby.—L. J. Spencer: A Butterfly Twin of Gypsum. In a well-developed twin- erystal, 6inches across, from Girgenti, Sicily, in which the twin- plane is d (101), the two individuals are situated on the same side of the twin-plane instead of on opposite sides as in the usual type.— Dr. W. R. Jones: The Alteration of Tourmaline. In a moist tropical climate minerals which are ordinarily regarded as stable break down to an extraordinary degree. At Gunong Bakau, Federated Malay Reports & Proceedings— Geological Society of Glasgow. 2389 States, tourmaline is found more or less completely altered to a mica (probably phlogopite) and limonite, the degree of alteration decreasing with increasing depth from the surface, suggesting that the change was caused by the percolation of water from above. The freshness of tourmaline grains in sands is very probably due to the removal of the altered products by chemical and mechanical means. Il1.—Gzrotoeican Socrrry or Guascow. Votcanozs in AyrsHire.—At a meeting of the Geological Society of Glasgow, held on March 9, Mr. G. V. Wilson, H.M. Geological Survey, read ‘‘ Preliminary Notes on the Volcanic Necks of North- West Ayrshire’’. The area dealt with lies between Dalry, Ardrossan, and Largs, and has been found to contain the remnants of about thirty voleanoes. ‘The various necks were described, and it was pointed out that they were not all of the same age. While some are probably of Caleiferous Sandstone age and connected with the great Misty Law volcano further north, others were much later as they contained large blocks of sedimentary rocks, including one with a coal-seam which was large enough to be worked within the vent many years ago. This vent must therefore have been in action after the formation of the coals of early Carboniferous times. Fragments of charred wood also occurred, while in one instance sea-shells, which had evidently been washed from the sea-floor directly into the voleano, were found. This showed that the volcano had been either submarine or on low ground liable to submergence, and the shells being of a type not later than Millstone Grit, the age of the vent was approximately fixed thereby. It was pointed out that the ash in the necks was, in some instances, very similar to that which replaces the black-band ironstone over much of the Dalry district, which suggested that it had come from this source, and that activity had continued intermittently until Millstone Grit or later times. It was suggested that in the days of its activity this district had resembled the San Franciscan volcanic field of Arizona. The paper was illustrated by a series of photo- micrographs and views. Mr. J. V. Harrison, B.Sc., described a section at Tormore, Arran, showing the junction of the two red rock series of Arran, and where no sharp line of division was visible. CORRESPON DEHN CE. > THE GRAINSGILL GREISEN OF CARROCK FELL. Srr,—Among a collection sent to me last year of small specimens from various well-known rocks in the British Isles was one of the -Grainsgill Greisen, Carrock Fell, described in vol. li of the Q.J.G.S. by Mr. A. Harker. For purposes of comparison with local rocks I have had three sections prepared from this specimen, which was only about 14in. square and } in. thick, and used the remainder for separations in heavy liquids. The quantity of rock available was so 240 Correspondence—J. B. Scrivenor. small that it is impossible to base any conclusions on the examination, but the following notes may be of interest to anyone who has time and opportunity to examine larger specimens. The most interesting point observed in my specimen is the abundance of rutile, in the form of ‘‘ sagenite webs’’, in the mica. A separation of powdered rock in a liquid of 2°8 sp.g. afforded a lot of them. They are visible in the slides too, but their abundance is only appreciated in preparations where the mica flakes are lying flat. In addition to rutile I obtained a few grains of brookite and one crystal that resembles anatase. One little plate of brookite, with clear erystal outline, gave a good axial figure. This unfortunately was either lost or turned on edge when mounting the heavy minerals in balsam, but two other minute grains give figures with a 14 in. oil immersion objective. With regard to the origin of the small-flaked mica I am inclined to think it is certainly derived from the felspar, of which I was able to separate enough for two microscope preparations, and there is evidence too of some of the large-flaked mica being derived from felspar. With regard to that containing the sagenite webs, the latter are unusual in muscovite, in fact I do not remember ever seeing them, and their presence suggests that the mica may originally have been a dark mica which has become bleached, but not completely so. On the other hand, it might be argued against this that the mica containing the webs has an axial angle about equivalent to that of muscovite, but the idea that the rock originally contained a dark mica is strengthened by the fact that some of the quartz-grains enclose minute flakes of biotite. Apatite and zircon occur, and I found a few minute grains of a mineral like cassiterite. One showed a carmine pleochroism common in cassiterite, although not mentioned in textbooks. I was unable to prove anything, however, about these grains. Some may be sphene. I found two grains of tourmaline, and tested the mica for lithia with negative result. J. B. Scrrvewor. GEOLOGIST’S OFFICE, BATU GAJAH. March 2, 1916. MISCHIUMANHOUS. Tue Zootocicat Recorp For 1914. This work has made its appearance a little later than usual owing to the difficulty in getting some of the literature. The volume for 1915 is well in hand, and it is hoped will be ready by next Christmas. At present it is the only work of reference from which one can gather the paleontological results of the year. The part containing any special group of animals can be had separately from the publishers, the Zoological Society of London. ee ee en ee ee VOLUME Il. Just PUBLISHED. THE DEPOSITS OF THE USEFUL MINERALS AND ROCKS: Their Origin, Form, and Content. By Dr. F. BEYSCHLAG, Prof. J. H. L. VOGT, and Dr. P. KRUSCH. Translated by 8. J. TRuscor, Associate Royal School of Mines, London. VOL. If: Lodes— Metasomatic Deposits — Ore-Beds — Gravel Deposits. With 176 Illustrations. 8vo. 20s. net. . : : Previously pwblished : VOL. I : Ore-Deposits in General—Masmatic Segregations—Contact - Deposits — Tin Lodes — Quicksilver Lodes. 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ORIGINAL ARTICLES. Page New or Imperfectly Known Chalk Polyzoa. By R. M. BRYDONE, _E.G.S. The Structure and Later Geological History of New Zealand. By SDI Oa oAc .COTTON, allen Le S v. No. VI.—JUNE, 1916. JUN 17 1916 ORIGINAL ARTICLES. Ws ' Tea “Honal Musew™ I.—NoreEs oN NEW OR IMPERFECTLY KNOWN CHALK Potyzoa. By R. M. Bryvons, F.G.S. (Continued from the March Number, p. 100.) PLATE X. MEMBRANIPORA MISSILIS, sp. nov. (PI. X, Figs. 1, 2.) Zoarium unilaminate, adherent. Zoecia strongly pyriporiform, very small, length about -4 mm.; areas broadly speaking elliptical but with a strong tendency to have the upper end flattened rather askew to the central line, average length "18mm., breadth -11mm.; the side walls of the area bear about a dozen tubercles so small that their existence is only just recognizable under a 38 in. objective; a 1 in. objective shows them to be perforated ; below the area there is typically (after the early stages) a small perforated boss placed centrally on the front wall, but when the front wall has to accommodate an ocecium the boss splits into two, often very massive, one on either side of the ocecium. Owcia very large in proportion, globular but tending to end in a definite but blunt point like an artillery shell; free edge narrowly and deeply concave. : _ Avicularia vicarious, fairly numerous, consisting of a shallow and wide pan with a small rounded aperture at the lower end; over the lower part of this aperture the side walls are sharply pinched in. This species appears in the zone of Marsupites in Hants and Sussex, where it is rare, and also occurs very sparingly in the zones of Offaster pilula and But see P. G. Morgan, ‘‘ The Geology of the Mikonui Subdivision, North Westland,’’ N.Z. Geol. Sury., Bull. 6, 1908, p.43; and also R. Speight, ** The Mount Arrowsmith District: Physiography,’’ Trans. N:Z. Inst., vol. xliii, pp- 319-20, 1911; ‘‘ The Intermontane Basins of Canterbury,’’ ibid., vol. xlvii, pp. 336-53 (p. 353), 1915. . ik 244 Dr. C. A. Cotton—Later Geological The folds of this system have sometimes been regarded as trending uniformly north-east and south-west parallel with the elongation of the existing ranges in which the rocks occur,‘ and from this it might be inferred that they determine the north-east and south-west trend NORTH ISLAND Kaikoura lauuR. HurunuiR SOUTH ISLAND ky Lake . WaitakiR RR) Manso. Oamaru hate VE ora bd; Shag R. b4 7 Tatert 2, Fic. 1.—Locality map of New Zealand. 1 See, for example, P. Marshall, ‘“New Zealand and Adjacent Islands,’’ Handbuch der regionalen Geologie, Bd. vii, Abt. i, p. 58, Heidelberg, 1911 ; Geology of New Zealand, Wellington, 1912, p. 127. History of New Zealand. 245 of the land masses of the South Island and the southern part of the North Island, an inference that has apparently been drawn by Gregory, who includes the coasts of Central New Zealand with those of his ‘primary Pacific type’’?. Such an inference is probably not true for any part of the coast of New Zealand. In the southern part of the North Island—in the vicinity of Wellington, for example—the discordance of the trend of the folds with that of the shore-line is shown clearly by the en echelon arrangement of the ridges which may be noted from any high point of view, ridge after ridge and valley after valley of the subsequent features developed by erosion on these strata being obliquely truncated by the western coast. The trend of the ridges, corresponding with the general direction of the strike of the rocks, is only 10° to 15° east of north, while that of the coast is north-east, parallel with the elongation both of the mountainous axis of the island and of the land mass as a whole. Some of the north-east trending coasts of Central New Zealand have recently been described by the writer as resulting from faulting of comparatively modern date.? In the South Island there appears to be by no means a close agreement between the trend of the major features and that of the folds of the oldermass. Scattered observation of the strike made by the writer in the north-east of the island show that it is very variable, but the average trend appears to be the west of north. Observations by McKay in the same district also indicate great variability,® and both McKay * and Hutton ® have noted a more or less definite dome and basin structure. In the main ranges of the Southern Alps the average strike of the rocks was noted by Dobson to be N. 22° E. (fide Haast). Haast ® and later observers, particularly Morgan” and Speight,® record great variability in that area also. In the study of the major relief features of New Zealand the trend of the Mesozoic folds may be almost entirely disregarded, for these features have been blocked out by much later orogenic movements, and the deformed strata of the oldermass, when affected by the latter movements, have generally behaved like resistant massive rocks. 1 J. W. Gregory, ‘‘ The Structural and Petrographic Classification of Coast Types © : : Scientia, vol. xi, pp. 36-63, 1912. 2 ** Fault Coasts in New Zealand ’’: Geog. Rev., vol. i, pp. 20-47, 1916. > A. McKay, ‘‘On the Geology of the East Part of Marlborough, Cole Mus. and Geol. Surv. N.Z., Rep. Geol. Expl., 1885, pp. 27-136, 1886; “On the Geology of Marlborough and South-East Nelson,” ibid., 1888-9, pp. 85-185, 1890. 4 F. W. Hutton, ‘‘ Report on the Geology of the North-East Portion of the South Island ’’: Col. Mus. and Geol. Surv. N.Z., Rep. Geol. Expl., 1873-4, pp. 27-58, 1877 (p. 32). ° A. McKay, ‘‘On the Older Sedimentary Rocks of Ashley and Amuri Counties’’: Col. Mus. and Geol. Surv. N.Z., Rep. Geol. Expl., 1879-80, PP. 83-107, 1881 (p. 85). ® J. von Haast, Geology of the Provinces of Canterbury and Westland, Christchurch, 1879. eG: Morgan, “The GUD ey. of the Mikonui Subdivision, North West- land,’’? N.Z. Geol. Surv., Bull. 6, 1908; ‘‘ A Note on the Structure of the Southern Alps,”’ Trans. N.Z. nae "vol. xliii, pp. 275-8 (p. 277), 1911. 8 R. Speight, ‘‘ The Mount Arrowsmith District : Physiography ’’: Trans. N.Z. Inst., vol. xliii, pp. 317-42 (p. 319), 1911. 246 Dr. C. A. Cotton—Later Geological A Perrrop or Erosion AND DeEposttion FOLLOWING THE Mxsozorc Orogenic Movements. Upon the eroded surface of the oldermass lies a series of covering strata, and there can be no doubt that the mountain ranges which resulted from the Mesozoic orogenic movements had been subjected to erosion throughout a long period and reduced to at least moderate relief before the deposition of the oldest (Cretaceous) beds of this cover. It remains uncertain, however, whether at this stage complete peneplanation had been effected over any considerable area. In North Canterbury, indeed, Speight! has noted changes of facies in the limestone horizon of the covering strata, and there is certainly overlap in the lower beds, indicating that the eroded surface of the oldermass was there still somewhat hilly when submergence began, and that some hills survived as islands during a portion of the period of deposition of the cover. The available evidence points, however, to practically complete submergence of a large part of the north- eastern district of the South Island in the period of deposition of the Amuri Limestone (perhaps Eocene), and in some parts much earlier. The open-water origin and wide original extension of the Amuri Limestone have been demonstrated by McKay * and Hector.* Hector’s brief statement may be quoted: ‘‘ All these formations enter into great flexures that have been eroded to form lofty mountains, and the evidence is complete that they at one time spread continuously over a wide area. ‘This view is therefore completely opposed to the suggestion that has been made that the upper calcareous members of the Waipara formation were deposited among islands and in land- locked inlets after the erosion of the present valley systems.” * In the Marlborough area there was a long period of uninterrupted deposition extending far into the Tertiary, though to what stage of the Tertiary is not yet satisfactorily established. At this juncture great but quite local uplift occurred in certain areas, probably by block faulting, leading to the deposition in the neighbouring un- disturbed areas of that remarkable formation the Great Marlborough Conglomerate.°® During the early part of the long period of deposition in Southern Marlborough the neighbouring Marlborough Sounds district to the north and the South-Western Wellington district to the north-east appear to have escaped submergence, for the basal portions of the few small remnants of covering strata, namely, a small area at -1 R. Speight, ‘‘ The Intermontane Basins of Canterbury’’: Trans. N.Z. Inst., vol. xlvii, p. 350, 1915. ° 2 A. McKay, ‘‘ On the Geology of the East Part of Marlborough,’’ Col. Mus. and Geol. Surv. N.Z., Rep. Geol. Expl., 1885, pp. 27-136, 1886; ‘*On the Geology of Marlborough and the Amuri District of Nelson,’’ ibid., 1888-9, pp. 85-185, 1890; ‘‘ On the Geology of Marlborough and South-East Nelson,”’ pt. ii, ibid., 1890-1, pp. 1-28, 1892 (see pp. 5-7). 3 J. Hector, Col. Mus. and Geol. Surv. N.Z., Progress Report for 1885, 1886 ; Progress Report for 1888-9, 1890. 4 Progress Report for 1885, p. xviii. 5 GC. A. Cotton, ‘‘ On the Relations of the Great Marlborough Conglomerate ... 7: Journ. Geol., vol. xxii, pp. 346-63, 1914. History of New Zealand. 247 Picton! and one in the Makara Valley, Wellington,” are regarded as of Tertiary age. The exposures are so poor in each case that the form of the surface on which the beds were deposited cannot be ascertained. We are not under the necessity of believing that the surface must by that time have been reduced to a plain, for it may have been rejuvenated from time to time by uplift, though adjoiming areas where deposition was in progress were sinking. It is quite possible that portions of these districts have never been submerged since first uplifted by the Mesozoic movements, though the seulpturing to which they owe their present mountainous character followed much later uplift. Planation may well have happened more than once in the long intervening period. North-eastward of Wellington there is no evidence of submergence having taken place until rather late Tertiary times.® Farther to the north, in the centre of the North Islands, Speight * notes the presence of a plateau surface truncating the structure of the oldermass in the Kaimanawa Mountains, which he ascribes to marine erosion. The surface presumably passes under and forms the floor of the Tertiary beds (referred to the Miocene) of that district, which occur up to the height of 8,700 feet above sea-level. It appears probable from Speight’s description that the covering strata were formerly continuous across the island in the Kaimanawa area, and that the plateau of the higher part of the range has been stripped of its cover by erosion. In the south-eastern and north-western parts of the South Island the covering strata, with the exception of some of the basal beds, are mainly marine and of such a nature as to indicate that they -accumulated in an open sea where the supply of terrigenous sediment was very small. Though the total area over which these rocks now occur is not large, their former extension over a much wider area is proved by the presence of outliers. _ From the above considerations and from a general survey of what is known of the Tertiary rocks it is apparent that during the period of their deposition a great part of the site of the present islands of New Zealand was continuously submerged, and that very little of the remainder was left above water. It is important to note that the members of the covering strata, whether always strictly conformable or otherwise, appear to follow one another without discordance of dip, no satisfactory evidence to the contrary being known. Thus it may be stated that, except quite locally,® the only movements affecting the region after the 1 A. McKay, Geol. Surv. N.Z., Rep. Geol. Expl., 1890, pp. 153-4. 2 A. McKay, ‘‘ Report on Tertiary Rocks at Makara’’: Col. Mus. and Geol. Surv. N.Z., Rep. Geol. Expl., 1874-6, p. 54, 1877. 3 J. A. Thomson, ‘‘ Mineral Prospects of the Maharahara District, Hawke’s Bay.’’: 8th Ann. Rep. Geol. Sury., Mines Statement, 1915, p. 165. 2 R. Speight, ‘‘ Geological History ’’ in L. Cockayne’s Report of a Botanical Survey of the Tongariro National Park, Department of Land, C. 11, Welling- ton, 1908, p. 7. 5 The hypothetical block movement which has been assumed in order to account for the Great Marlborough Conglomerate has been referred to on an earlier page. In a paper on the ‘‘ Structure of the Paparoa Range’’, read before the Geological Section of the Wellington Philosophical Society, 248 Dr. C. A. Cotton—Later Geological Mesozoie orogenic period until near the end of the Tertiary were epeirogenic. This is contrary to the view of Hutton,’ who believed that folding movements affected the Cretaceous rocks in early Tertiary times, before the deposition of the remainder of the covering strata. THe Kaikoura Orogentc Movements. The orogenic movements which followed the Tertiary deposition, and to which the present relief is entirely or almost entirely due, must have occurred in or about the Pliocene period. The period of movement may be termed the ‘‘ Kaikoura orogenic period ”, since the Kaikoura ranges were the first to be explained by Hector’ and McKay* as owing the whole of their elevation to these late earth- movements. It cannot, however, be definitely stated at present whether the- orogenic movements began contemporaneously all over the region. Far too little is known as yet of the ages and correlations of the members of the covering strata to allow us to arrive at a conclusion on this point. The immediate cause of the disturbance may have been compression, for, in Central New Zealand at least, compression in a north-west and south-east direction accompanied the movements. In Marlborough the uplifted and depressed areas are elongated with a north-easterly trend, and major faults, some of which are certainly reverse faults, trend in the same direction, as do also folds in the previously horizontal covering strata. Perhaps owing to the rigidity of the oldermass, the strata of which had previously been folded on other lines and would strongly resist the new folding, the region was broken up into a number of ‘blocks’ bounded on one or more sides by faults, folding being generally subordinate to faulting except in the higher members of the covering strata, where the resistance of the rigid floor had least effect. In recent years, wherever detailed geological work has been done, evidence has accumulated of the importance of the part played by young faults in the structure of New Zealand, as may be found by reference to the accounts of the structure of parts of Westland, Nelson, Otago, and Auckland by Bell, Morgan, Park, Henderson, and others in the bulletins of the Geological Survey, and to a paper by Henderson * in which much information regarding faults in Western Nelson is brought together. While in a few cases the recognition of these faults rests on the evidence of fault-scarps or fault-line scarps, the majority of the faults described are such as bring the covering strata against the older rocks. Many other faults less easily detected by purely geological August 18, 1915, Dr. J. Henderson stated that in Western Nelson a suc- cession of similar movements had taken place. In these cages, however, during and after the movement, accumulation of sediment went on in the immediate vicinity on an undisturbed sea-floor. 1 Geology of Otago, Dunedin, 1875, p. 76. * Progress Report, Rep. Geol. Expl., 1888-9, p. liv, 1890. > ‘*On the Geology of Marlborough and South-East Nelson,’’ pt. ii: Rep. Geol. Expl., 1890-1, p. 7, 1892. 2 dio Hendercen: On the Genesis of the Surface Forms and Present Drainage-systems of West Nelson ’’: Trans. N.Z. Inst., vol. xliii, pp. 306-15, 1911. History of New Zealand. 249 methods also occur. The long straight fault-lines shown on the map by McKay’ and the later maps by Park,? connecting up known portions of faults, must of necessity be highly hypothetical, and they probably fall far short of representing the facts; but it is true, never- theless, that to McKay belongs the credit of being the first to recognize the importance of faults in determining the Biya! features and geological boundaries. McKay’s views are strongly opposed to those of Hutton, who conceived only of regional (epeirogenic) movements of uplift and subsidence in later geological times.* Hutton recognized no young faults and no orogenic movements later than those at the close of the Jurassic except ‘‘a certain amount of folding” restricted to certain localities, which, he believed, took place ‘“‘at the commencement of the Tertiary ”.4 ‘* Not only,” he wrote, ‘‘ was the last touch given at this time commencement of the Tertiary] to the geological structure of the tSouthors Alps, but the chief valleys were also marked out at this period. ‘For example, we find our oldest tertiary rocks occupying the valley of the Waitaki . . . and the Maruwhenua ... Inthe valley of the Shag they extend up nearly to its source... .’° To the explanation of the geological history of New Zealand thus expressed in 1875 Hutton afterwards closely adhered, as will be gathered from the following statements as to supposed changes in river courses, which are based on the assumption that the present relief has survived from very ancient times. This represents Hutton’s opinion in 1899: ‘‘ The Shag River at one time drained the ‘Maniototo Plains until the gorge of the Upper Taieri was cut.. In early Cretaceous times the Hurunui and Waiau-ua united and entered the sea at Kaikoura. At. a later time they turned down the Weka Pass, and it was not until the Pliocene period that each cut its own valley to the sea. The Upper Manawatu flowed into the Wairarapa, and in the older Pliocene a river ran from the Manawatu gorge to Napier. The courses of all these rivers were changed by the deposition of marine rocks in the valleys, which blocked them; and this, on the subsequent rise of the land, caused the rivers to overflow to one or the other side, according to the position of the lowest opening.” ® The depressions, such as the Shag Valley and that extending from the Waiau to Kaikoura, regarded by Hutton as eroded valleys and assigned by him in the foregoing passage to ancient courses of various rivers, are more satisfactorily explained as tectonic features which came into existence in the Kaikoura period. 1 N.Z. Rep. Geol. Expl., 1892, p. 1. 2 J. Park, Geology of New Zealand, Christchurch, 1910, pp. 263, 265. * Geology of Otago, Dunedin, 1875, pp. 77-85 and pl. ii. * Loe. cit., p. 76. > Loc. cit., p. 77; cf. also ‘‘ Sketch of the Geology of New Zealand’’, Quart. Journ. Geol. Soc., vol. xli, p. 196, 1885. 6 ‘«The Geological History of New Zealand’’: Trans. N.Z. Inst., vol. xxxii, p. 180, 1900. (Lo be concluded im our next Number.) 250 Dr. Du Riche Preller—Crystalline Rocks of Piémont. I1I.—Tae Crrysrattine Rock AR®EAS OF THE Pr&MontESE ALPS. By C. 8S. Du RicHE PRELLER, M.A., Ph.D., M.I.H.E., F.G.S., F.R.S.H. (Concluded from May Number, p. 205.) : Ill. Tax Dora Riranra Grove. (Figs. 3 and 4.) |e this group, shown in the sketch-plan Fig. 4, may be included the interesting pietre verdi areas (1) of the Rocciavré ridge on the right, (2) of Monte Rocciamelone on the left side of the Dora Riparia Valley, and (3) of the Rocciacorba ridge and the Avigliana belt of spurs where the Dora and the Sangone Rivers emerge from the Alps and enter the Po Valley about 20 kilometres west of Turin. — 1. The Rocciavré Area.—This ridge, about 12 by 4 kilometres in length and width, forms the divide between the Dora Riparia and Chisone Valleys, north and south respectively, while its eastern end lies at the head of the short valley of the Sangone torrent which discharges into the Po at Moncalieri south of Turin. Although the ridge derives its name from Monte Rocciavré, the latter (2,778 m.) is only one and not the highest of a remarkable cluster of pietre verdi peaks ranging from 2,600 to 2,900 metres in altitude. Of these the most notable are Rocciavré, Cristalliera (2,801 m.), Pian Real (2,617 m.), and Rocca Rossa (2,891 m.) at the eastern, Gavia (2,841 m.), Rocca Nera (2,852 m.), and Mezzodi (2,777 m.) at the northern, and the highest peak Orsiera (2,878 m.) at the western end, the elevation thus decreasing from west to east. The whole ridge obviously represents a former extensive pietre verdi sheet or cupola cut up by erosion and atmospheric denudation into resistant peaks which are separated by high co/di or saddles of about 2,500 metres altitude. The high-level pietre verdi area is accessible either from Perosa in the Chisone Valley (700 m.) or from Bussoleno (500 m.) in the Dora Valley, on which latter side the flanks of the ridge are deeply cut by several torrents in cascade gullies or orrzdi.! On the Chisone or southern flanks one of the most remarkable exposures, pointed out by Gastaldi as early as 1876,” is that near Colle della Roussa, about 2,400 metres altitude, where the substratum of minute and tabular gneiss with intercalated crystalline limestone, steatite, and graphitic rock is overlain horizontally and conformably by a great bank of lherzolite more or less altered to serpentine, both compact and schistose, upon which rests an equally high bank of euphodite largely metamorphosed to amphibolic and epidotic rock with smaragdite, and to glaucophanic prasinites. The total thickness of this pietre verdi exposure is at least 200 metres. Unlike the southern or Chisone flanks, which form part of the gneissic-graphitic zone, the northern or Dora Riparia flanks of the ridge exhibit from Bussoleno (500 m.) upwards the normal 1 These cascade gullies, varying from 100 to 300 metres in height, are characteristic of the mountain-sides of the Dora Riparia Valley, and are locally called orridi both from their weird, forbidding appearance and the enormous quantities of detritus and débris brought down through them by the torrents when in flood. 2 Boll. R. Com. geol., 1876, p. 108. Fig. 2. SECTION OF MONTE VISO. iz GLE DAE CS OX St, | LOY Yin? ZPD é EX Ditye(geZ ZZ thn 1:(00,000. OLIN Sea level. Fig. 3. SECTION OF ROCCIAMELONE. NW, LL eS: am Rocccametone ZZ CS 100,000 ALLE, KGL Es fyzse eo bevel, C7, LG Z Fig. 4 THE DORA RIPARIA GROUP. kel fe Rocciavre, Rocciamelone, Rocciacorba and Avigliana. Roeciamel if Ue Wvigtcana Dore Morturnre PY e © PRocchavee A «(, “lly fo = il) I) as J Def DEP, cs = Calc-schist; cl = crystalline limestone; s = serpentine; e = euphodite; ~ axp = amphibolites and prasinites. Del. D.R.P. 252 Dr. Du Riche Preller—Crystalline Rocks of Prémont. crystalline sequence of mica-schist with gneiss intercalations at the lower, and cale-schists with pietre verdi at the higher levels. The Bussoleno gneisses, quarried on the right of the Dora down to Villar Foechiardo, differ greatly from the primitive, large-grained, glandular, eye-gneiss of the Dora—Maira massif which crops out on both sides of the valley from Villar Focchiardo to 8. Michele. Those younger, intercalated gneisses are of the minute and tabular type, in part with porphyroid and eye-structure, more or less tourmaliniferous, often rich in albite and poor in mica, or vice versa, while the mica-schist is frequently garnetiferous.! Such gneiss intercalations also occur higher up the ridge, where they are associated with omphacitic eclogite and prasinite. The pietre verdi area of the ridge as a whole may be described as composed of peridotitic, serpentinous, and euphoditic masses extending in the shape of a triangular trough from the Orsiera peak at the western to Colle della Roussa at the southern, and to Rocciavré, Pian Real, and Rocca Rossa at the eastern end, while euphodites and prasinites predominate more especially in the Rocca Nera and Mezzodi peaks in the centre of the northern part. The serpentinous masses reach their maximum thickness of about 300 metres in the Orsiera and of 500 metres in the Pian Real peak. The contact between serpentine, euphodite, and prasinite is generally marked by serpentinous, chloritic, and actinolitic schist, and in places by eclogite with large uralitized omphacite crystals, while the chloritic schist, e.g. between Pian Real and Rocca Rossa, contains diallagic, viz. smaragdite, crystals of unusually large size.” The euphodites present a great many varieties and are, as usual, largely altered to their pees and zoisitic derivatives. In the total rise of 2,300 metres from the valley floor near Bussoleno to the crest-line of the ridge, the garnetiferous mica-schists, with tourmaliniferous gneiss intercalations and quartzite, occupy about 1,200 metres, followed by about 600 metres of cale-schist with intercalated prasinitic and serpentinous schist, and lastly by about 500 metres of pietre verdi forming the cupola of the ridge. The ravine of the Sangone east of the ridge to Giaveno, where the torrent enters the Po Valley, is deeply and entirely eroded in the gneiss and mica-schist of the Dora—Maira massif without pietre verdi, but in other directions the Rocciavré group is linked with large pietre verdi areas both past and present. Thus, on the north the pietre verdi extend across the Dora Valley to Rocciamelone and the Lanzo valleys, while west, south-west, and south a large number of small intermittent outcrops afford evidence of a former extensive area which lay in the great syncline of the calc-schist formation 20 to 25 kilometres in 1 The gneisses of Bussoleno are among those regarded by Professor Gregory as intrusive and Pliocene (‘‘ Waldensian Gneisses ” : Q.J.G.S., 1894, p. 232 et seq.). His views were traversed in detail by Franchi, si Appunti Monti di Bussoleno’’: Boll. R. Com. geol., 1895, p. 177 et seq., and by Novarese, ‘* Rilevamento Valle Germanasca ’’ : ibid., 1895, p. 277 et seq.; also by Stella, ‘‘ Valli Oreo e Soana’’: ibid., 1894, p. 349, footnote. 2 Franchi mentions such crystals up to 50 ‘centimetres in length. Op. cit., 1895, p. 3 et seq. , 7 ; » Dr. Du Riche Preller—Orystalline Rocks of Prémont. 258 width,! and connected the Rocciavré group with the similar groups of Oulx, Chaberton, Genévre, Maurin, Chabriére, and Monte Viso. 2. The Rocciamelone Area.—This imposing mountain, the ancient Mons Romuleus, with its peaked summit rises straight from the Dora Riparia on the right of the valley at Susa (503 m.) to an altitude of 3,537 metres in a horizontal distance of only 7 kilometres. The most accessible ascent is from Susa or, further down the valley, from Bussoleno. The massif lies in the calc-schist horizon, which also includes the series of similar high peaks immediately north of it, as far as the Levanna and Gran Paradiso gneiss massif. From the summit and the sanctuary of Madonna della Neve down the southern flank the cale-schist alternates at first with micaceous schist, lenticular masses of bluish and white crystalline limestone, serpentine with ophicalce or ‘green marble, and amphibolites and prasinites, as far as the spur of Tre Cresti. From this point in an oblique direction towards Bussoleno and Chianoc, the alternations of calc- and micaceous schist with pietre verdi become more frequent, and nearer the valley floor are replaced by minute and tabular gneiss, intercalated masses of erystalline limestones, and the fossiliferous calcareous beds of Chianoc and Foresto. On this southern flank, shown in the section Fig. 3, the pietre verdi exhibit remarkable aggregations of amphibolic and prasinitic rocks with both massive and schistose serpentine, which latter becomes so predominant as to eclipse the calc-schist altogether. Especially is this the case in and above the Rio Muletta gorge, which descends to Bussoleno from the Croce di Ferro ridge, and exhibits an almost perpendicular cliff of serpentine no less than 500 metres in height, overlain by another 500 metres of amphibolites and prasinites. The serpentine cliff rests on crystalline limestone which then alternates with calc- and serpentine-schist down to the minute and tabular gneiss near Chianoc, the latter belonging to the same horizon as the Bussoleno gneisses on the opposite side of the valley. Lower down the valley, as already mentioned, the typical primitive, glandular gneiss with large elements and greyish-green mica appears on both sides, extending on the left to St. Didero, Borgone, and Condové, and on the right to St. Antonino, Vayes, and the chiusa or defile of S. Michele. In this section of about 12 kilometres the bed of the Dora Riparia is therefore eroded entirely in primitive gneiss, which here forms the northern extremity of the Dora—Maira gneiss massif. The crest of the great ridge of peaks and crags which runs on the left of the Dora from Rocciamelone eastward for about 36 kilometres to the spur of Monte Musiné, north-east of Avigliana, is almost entirely composed of pietre verdi with only a few narrow outcrops of eale-schist in the intervening eroded saddles or colli. As this ridge forms more properly part of the area of the Lanzo valleys, I shall refer to if again in connexion with that region. 1 The cale-schist formation extends north-west, and entirely encircles the mica-schist and minute gneiss massif of Rocca d’Ambin (3,377 m.), about 20 by 10 kilometres in length and width, which lies between the upper Dora Riparia Valley on the Italian and the Are Valley on the French side, and at its northern extremity is crossed by the Mont Cenis road from Lanslebourg fo Susa. ; 254 Dr. Du Riche Preller—Crystalline Rocks of Piémont. 8. The Rocciacorba and Avigliana Area (Fig. 4).—This area is of special interest, owing alike to its complex nature and its singular configuration, and also because of its vicinity to Turin, whence it is easily reached by Rivoli, Giaveno, or Avigliana. As already mentioned, the eastern spurs of the Dora Riparia and Sangone Valleys converge to a horseshoe or amphitheatre—about 25 kilometres in circumference and 10 kilometres in width—in the centre of which lies Avigliana. The southern end of the horseshoe, on the right of the Sangone, is formed by the Pietraborga spur (926m.) of the Rocciacorba ridge, the middle or western part by the Ciabergia (1,178 m.) and Sacra S. Michele (962 m.) spurs between the Sangone and Dora Riparia Valleys, and the northern bend, on the left of the Dora, by the promontory of Torre del Colle (600 m.), and the mountain-side comprising, among others, Rocca della Sella (1,508 m.), Monte Curto (1,825 m.), and, at the eastern extremity, Monte Musiné (1,150 m.). Across the centre of the horseshoe, as a connecting link between the Pietraborga and Torre del Colle spurs, stretches the low Moncumi (642 m.) and Avigliana ridge, and between this and the Ciabergia or western spur lie, in an old morainic depression, the two small lakes of Avigliana (452m.). From the Moncumi ridge eastward spread the enormous glacial and alluvial deposits of the Dora Riparia, sloping down towards Rivoli and Turin.’ On the rugged and precipitous flanks of the horseshoe, patches of glacial deposits reach up to 900 metres altitude or 500 metres above the valley floor, but the continuity of the rock formations can be traced all round the crags and in the numerous gullies or orrzdz of the different spurs. The pietre verdi of this area lie in the horizon of minute gneiss and mica-schists, which are, however, in evidence only in outcrops on the western margin, at the base of the primitive gneiss, and therefore in reversed sequence, as the continuation of the corresponding reversal further south, already referred to. The minute gneiss and mica- schists with crystalline limestone form banks of considerable thickness on the Ciabergia and 8. Michele ridge where they are quarried. Together with the pietre verdi on their eastern margin, they are the continuation of the gneissic, dioritic, and peridotitic belt of the Roccia- corba ridge, which, about 8 by 3 kilometres in length and width and about 900 metres in altitude, extends from Monte S. Giorgio, near Piossasco, on the south, to the Pietraborga spur above Trana at its northern end. The crest-line of this ridge exhibits in succession the masses of garnetiferous and graphitic mica-schist and minute gneiss, lherzolite, serpentine, and dioritie rocks with associated eclogite, and amphibolic and prasinitic schists which constitute the series and reach their greatest thickness in Monte Montagnazza (892 m.). From the Pietraborga spur the pietre verdi radiate N.W., N., and N.E. in several more or less defined zones, of which the western follows the Ciabergia ridge, crosses the Dora Riparia at 8. Michele, and reappears on the left bank at Chiayrié, while the middle zone, starting from the same point, forms the Moncumiand Avigliana ridge 1 Of this ‘‘ Morainic Amphitheatre of Rivoli’”’, Professor F. Sacco has given an interesting description in Boll. R. Com. geol., 1887, p. 141 et seq. Dr. W. R. Jones—Topaz and Cassiterite in Malaya. 255 between the Sangone and the Dora, and reappears on the left of the latter at Torre del Colle; andathird zone, bifurcating from the second at the Moncumiridge, crosses the Dora, and, running north-east, forms the Musiné spur. Within the Avigliana horseshoe, the pietre verdi thus attain a visible thickness of 500 metres in Monte Pietraborga, of 700 metres in the Ciabergia ridge, and of 1,200 metres and more on the mountain-side left of the Dora, whence the series continues north for about 25 kilometres along the eastern spurs to Lanzo. It is in this belt that the peridotitic masses, lherzolite and serpentine, with associated euphodite, are more especially predominant. In places, e.g. in the Musiné spur, the lherzolite is so decomposed that it is quarried for the extraction of magnesite.! All the pietre verdi masses of the Rocciacorba and Avigliana area dip at more or less steep angles, in some places are almost vertical, and throughout are much contorted. The three groups of the Dora Riparia area, viz. of Rocciavré, Rocciamelone (in the triangle Susa, Chianoc, and summit) and Avigliana, including Rocciacorba, cover each about 50, in the aggregate 150 square kilometres, or about 60 square miles, equal to the superficial area of the Monte Viso group. The conclusions as to the age and origin of the pietre verdi groups of Southern and Western Piémont considered in the present paper, will be stated in connexion with the areas of Northern Piémont to be dealt with in the sequel. 1V.—TuHeE Ortern or Toraz anp CassIreRIrE at Gunone Baxkav, Mauaya. By WILLIAM R. JonzES, D.Sc. (Lond.), F.G.S. NOPAZ is commonly supposed to have been formed by the action of fluorine-bearing vapours on felspar, but evidence has recently been advanced with the object of showing that some important veins ‘intrusive in the porphyritic granite of Gunong Bakau, a mountain 4,426 feet high, situated in the centre of the Main Granite Range of the Malay Peninsula, were formed of a rock in which ‘‘ the topaz and cassiterite are not alteration products of previously formed minerals”. The author of this theory gives the rock the descriptive name of ‘ quartz-topaz’, and adds as his reasons for not calling it ‘greisen’ the fact that in places it contains very little mica and that, unlike the majority of greisens, it is not an alteration product. The writer is very familiar with the area in which these rocks occur, and in a report® written in 1913 called attention, for the 1 The quarried exposure of lherzolite with euphodite and magnesite is on the south-east slope of Monte Musiné, above Casellette (505 m.). About 8 kilom. east of this point, midway between it and Turin, lies, at Pianezza, in the morainiec area, Roc Gastaldi, an erratic monster-block of euphodite measuring 30 by 12 by 14 metres in length, width, and height = 5,000 cubic metres or over 10,000 tons. It is surmounted by a small chapel. 2 J.B. Scrivenor, ‘‘ The Topaz-bearing Rocks of Gunong Bakau’’: Q.J.G.S., vol. lxx, p. 363, 1914. 3 W.R. Jones, Preliminary Report of Mining in the Main Granite Range, Federated Malay States, 1913. 256 Dr. W. R. Jones—Topaz and Cassiterite 1n Malaya. first time, to their importance as a source of tin-ore. The object of the present paper is to adduce evidence in support of the generally accepted theory for the origin of this topaz and cassiterite, and against that of their primary origin. It is not suggested that topaz and cassiterite never occur as primary minerals, for cases are known where the evidence appears conclusive that they can so occur on a small scale, but for the present attention will be confined to this particular locality, where the occurrence is on a large scale and of economic importance. The veins of ‘ quartz-topaz’ vary in thickness from about 15 feet to less than an inch, and in some places have now been extensively worked for tin-ore, notably on the mines of Messrs. Bibby and Ruxton and adjoining mines. The difficulties against accepting the ordinary theory for the | genesis of the topaz in these veins are clearly set forth by the author of the paper referred to, and may be summarized as follows: the absence of alteration in the country rock ; the dissimilarity between the vein rock and rock in the same locality that is clearly an alteration rock ; the presence in some of the rock of an iron-rich zinnwaldite which is different from the neighbouring secondary mica; the marked difference between the tin-ore bodies known to be of secondary origin and the bodies of ore in these veins. The absence of alteration in the country rock in the locality under consideration does not appear to be more pronounced than in other tin-fields where topaz and cassiterite have clearly been shown to be of secondary origin. The dark borders to these veins are stated to be ‘‘the result of reaction between media that came off from the vein rock and the porphyritic granite, and a portion of the original vein rock’’,! and to contain a little topaz and an abundance of tourmaline. Also the granite country rock ‘‘is altered for a few inches by emanations from the vein rock to form familiar pneumato- lytic modifications’’.? This alteration is certainly as extensive as is the case in places at Geyer and Khrenfriedersdorf, areas in the Erzgebirge tin-field, for there the alteration of the country rock is for a distance of only 2 to 6 inches,* whereas in the Graupen area the country rock of the Luxer cassiterite-bearing vein has not been altered at all into greisen.t That the topaz and cassiterite of the Erzgebirge tin-field is of secondary origin has been very con- clusively established, for the mine exposures in Altenberg Zwitterstock show ‘‘that the impregnation has been confined to the upper portion of the granite”’, and that ‘‘at a depth of 700 feet normal granite is encountered, in which zwitter bands are completely lacking or only sparingly present ”’.® The writer’s observations of various tin-lodes have led him to the conclusion that the amount of alteration of the country rock is 1 J. B. Scrivenor, op. cit-, p. 370. 2 Tbid., p. 375. 3 J. T. Singewald, jun., ‘‘ The Erzgebirge Tin Deposits ’’ : Hconomic Geology, vol. v, p. 267, 1910. 4 Tbid., p. 177. SV Tbidi pigevaes f ak we i Dr. W. k. Jones—Topaz and Cassiterite in Malaya. 257 sometimes extremely irregular even in the same vein, but is greatest, in general, where the rock contains a network of small fissures filled with ore. There are, however, exceptions to this, for at the Chendai and Menglembu lode-veins in Kinta, Malaya, where felspar crystals -are cut by minute cassiterite-bearing fissures, the felspars, as has been previously pointed out by Mr. Scrivenor,'are quite fresh. The writer saw an interesting case at Serendah, Malaya, where the absence of alteration in the country rock of a lode appeared to be due to its coalescence with another lode, exposed later, and through which the mineralizing vapours found an easier conduit. The dissimilarity between the vein rock and the adjacent alteration rock is only what would be expected, for the rock intruded as veins in the consolidating granite was the more acid part of the differentiated magma and formed, before being subsequently acted upon by an abundance of fluoriferous mineralizers, an aplite or pegmatite vein rich in quartz, felspar, and little or much mica, such as are so very frequent in this neighbourhood. It is not the rule, but rather the exception, to find the peripheries of cassiterite-bearing veins similar in mineral content to the central parts of the vein, especially where the veins are thick. The footwalls of tin-lodes are, in general, richer in ore than the hanging walls and very considerably richer than in the body of the lode; and where wolfram, for example, occurs associated with tin-ore the former frequently occurs sporadically as coarse crystals along the walls. At Zinnwald? quartz and zinnwaldite occur in a lode as layers in such a way that the individual layers are parallel to the walls, and one of these may occur to the almost complete exclusion of the other. The presence in these ‘ quartz-topaz’ veins of an iron-rich zinnwaldite seems to support, rather than contradict, the secondary origin of the topaz and the cassiterite, for zinnwaldite is also abundant in the veins in the Erzgebirge tin-field. At Zinnwald in this district ‘‘the chief gangue minerals are quartz and zinnwaldite’’.* It will also be shown later that the addition of iron takes place in the process of greisenization in districts where chemical analyses of the greisen and the unaltered rock are available. Emphasis is given to the marked difference between the ore-bodies occurring at Gunong Bakau, admitted to be of secondary origin, and the ore-bodies in the veins where the topaz and cassiterite are presumed to be of primary origin. The ore-bodies worked at Gunong Bakau occur mainly in four types of lodes: (1) The rock at Hemy’s Lode, which has been described elsewhere* by the writer, is not sufficiently coarse-grained for a typical pegmatite, and although more acid than ordinary granite, is best described as an altered medium- grained granite, very rich in quartz, mica (some being secondary), tourmaline, and cassiterite, relatively poor in felspar, and containing 1 J. B. Scrivenor, The Geology and Mining Industry of Kinta District, Federated Malay States (Kuala Lampur), 1918, p. 62. 2 J.T. Singewald, jun., ‘‘ The Erzgebirge Tin Deposits’’: Hconomic Geology, vol. v, p. 173, 1910. > Thid. 4 W. RB. Jones, ‘‘ Mineralization in Malaya’’: Min. Mag., vol. xiii, No. 4, p. 198, Oct. 1915. DECADE VI.—VOL. III.—NO. VI. 17 ( 258 Dr. W. R. Jones—Topaz and Cassiterite in Malaya. a little fluorite; (2) the ‘quartz-topaz’ rock carrying tin-ore and (3) the ‘topaz-aplite’ at Messrs. Bibby & Ruxton’s mine; (4) pegmatite veins, composed mainly of milky quartz, in mines near by. The differences in the gangue of these lodes do not appear to be more striking than in numerous other areas in Malaya and in other tin-fields, and not even so marked as in some. It might even be said that variations equally great have been observed elsewhere in different parts of even the same lode. ‘The Luxer! vein at Graupen in the Erzgebirge tin-field, for example, is characterized by extremely variable filling. The prevailing gangue is milk-white quartz which locally gives place to coarsely crystallized orthoclase intergrown with albite, and to fluorite; also a dark-green lithia mica and a compact variety of kaolinite (‘steinmark’) occur as subordinate gangue minerals ; and the cassiterite is usually evenly distributed, as in the Gunong Bakau veins. At Zinnwald, in the same tin-field, sulphides are confined solely to the middle of the veins, and the tin-lodes contain as essential constituents quartz and a greenish or brownish-green mica, whereas in the neighbouring area of Altenberg topaz is the predominant constituent. In this tin-field at Sadisdorf a lode?” formerly worked for tin-ore is now worked solely for wolfram and molybdenite. Near the footwall occur large nests of pure wolfram, which together with the enclosing quartz are cut by secondary horizontal stringers of quartz carrying tin-ore and gilberite. These stringers are again cut by still younger vertical fluorspar stringers, and towards the hanging wall a great deal of molybdenite and also a little zinnwaldite are encountered, and bismuth and bismuthine also occur along both walls. . All the types of rocks found at Gunong Bakau in Malaya are also found in some other tin-fields, notably the Erzgebirge tin-fields, where ‘‘all stages of transformation from granite to greisen are encountered and frequently the greisen areas include unaltered masses of granite’’.* At Geyer the granite is locally converted to a rock containing more than 90 per cent of topaz.‘ It is stated by Mr. Scrivenor ‘‘ that the sequence of events in the mass forming Gunong Bakau is clear. First the porphyritic granite consolidated; then the quartz-topaz veins were intruded; and then the topaz-aplite arrived’’.> If the topaz in the quartz-topaz veins is a primary mineral the differentiation of the original magma must have taken place under extraordinary conditions, for a rock, free from felspar, is supposed to have been intruded after the first, containing porphyritic crystals of felspar, and before the third, which is described as being ‘‘rich in felspar’”’. The absence of felspar in the second intruded rock is explained by supposing that ‘‘in the depths of the igneous mass there was a magma which, if undisturbed, would have crystallized out as a rock composed chiefly of potash 1 J. T. Singewald, jun., ‘‘ The Erzgebirge Tin Deposits ’’: Hconomic Geology, vol. v, pp. 176-7, 1910. 2 Thid., p. 169. 3 Ibid., p. 174. 4 Solomon & His, Zeit. deutsch. geol. Ges., vol. xl, p. 250, 1888. 5 J.B. Serivenor, ‘‘ The Topaz-bearing Rocks of Gunong Bakau’’: Q.J.G.S., vol. lxx, p. 378. a a Dr. W. R. Jones—Topaz and Cassiterite in Malaya. 259 felspar”’.! This magma was then invaded by ‘‘a volume of gas. as a huge bubble rising from below, where st had been collected in a part of the magma on which it could not react”, and attacked ‘‘eroups of molecules that would have solidified as felspar if they had not been disturbed by hydrofluoric acid’’? (italics inserted, W.R.J.). The writer will not enter here into the question of the miscibility of silicate minerals in a magma which was sufficiently mobile to be intruded through long narrow veins, some less than an inch thick, nor on the possibility, or otherwise, of the accumulation of a huge bubble of vapour in the depths of an igneous mass, but will point out that no explanation is given of how a highly fluori- ferous vapour can collect in a part of a magma on which it could not react. Moreover, a salic magma depends for its fluidity, as Bowen states,> ‘‘on its ability to retain volatile constituents,” and the presence in such a magma of a free oxide, such as cassiterite, does not appear to be possible.* Especially is this the case in a magma which later emanated hydrofluoric acid. In a footnote to p. 379 of his paper on these rocks the author has raised a question of great interest. He points out that ‘‘ without segregation one could not expect to have a rock very rich in topaz’’, and gives figures to show that with a pure orthoclase magma only 32°6 per cent of topaz could be formed. There is, however, an explanation why the percentage of topaz in a greisen does not necessarily depend on the percentage of felspar in the original rock. Researches on greisenization have shown that where it has been possible to obtain analyses of greisens and their neighbouring granites, some of the chemical changes involved appear to be as follows :— According to Addition of Abstraction of Vogt.’ Si Oo, Be Os, F (or HF), Sn On, ; CaO, MgO, NagO, and often often also LigO, K2O, and also K20O, Ale Os. perhaps Al O3. Dalmer.® FeO, F, Sn Oz, and possibly | K,0, Nag O, Si Ox. Ale Os. i Cotton.” Si O02, FeO, MgO, Sn Oz, — Mo Se, Als Os. Jones, W. BR. | Ale Oz, Sn Oo, Be Os, HF, | KeO, Nag O. : Lig O, and possibly Si Oe. ? J. B. Serivenor, ‘‘ The Topaz-bearing Rocks of Gunong Bakau’’: Q.J.G.S., vol. lxx, p. 379. 2 J. B. Scrivenor, Mining Magazine, February, 1916, ‘‘ Discussion.” ° N. L. Bowen, “‘ The Later Stages of the Evolution of the Igneous Rock’? : Journal of Geology, supplement to vol. xxiii, No. 8, p. 16, 1915. * A. Harker, The Natural History of Igneous Rocks (London, 1909), p. 166. ° J. H. L. Vogt, ‘‘ Beitrige zur genetische Classification der durch magma- tische Differentiationprocesse und der durch Pneumatolyse instanden Erzyo- kommen’: Zeit. prak. Geol., 1895, p. 146. * K. Dalmer, “‘ Der Alterberger-Graupener Zinnerslagerstittendistrikt ’” : Zeit. prak. Geol., 1894, p. 319. 7L. A. Cotton, ‘‘ Metasomatic Processes in a Fissure Vein from New England’’: Proc. Linn. Soc. New South Wales, p. 231. 260 3=G. C. Crick—Gigantic Cephalopod Mandible. Messrs. Fergusson and Bateman,’ as a result of their recent researches on greisenization from different localities, have come to the general conclusion that in the chemical changes involved there is an increase in silica, aluminium (which is only in part Al, O.), and probably of iron oxides, a loss of lime, magnesia, and the alkalies, the losses of the alkalies being approximately in proportion to the amount of each originally present, and only in slight degree selective. The following figures, extracted from analyses of granite and greisens, are instructive. In the cases of veins, the granite country rock would probably, however, be less acid than the former before greisenization. NEw SouTH WALES.2 ERZGEBIRGE.® GUNONG BAKAU, MATLAYA. Grei Grei Grei é Grei < Unaltered eae Hous a Unaltered Caney pees Unaltered (quakes: aoe Granite. | from vein | Granite. | mica, oe a ‘| Granite. | mica, os aay vein. wall, topaz), | 0P42/. topaz), | 0P22)- SiOg .| 76:69 | 75-42) 78-47| 74-68 | 70-41] 79-73 | 77-12 | 77-50 | 80-08 AlgO3 .| 10-89 | 12-98] 11-50] 12-73 | 13-06") 10-244 11-07 | 13-01 | 12-45 Fee O3 0:76 1:68 | 2-64 — 1-42 \ Air75) | “015 N05 FeO, 0-39 | 0-58] 1-05] 3-00 | 5-09 j Te ae etc. CoNncLusIon. The topaz-bearing rocks of Gunong Bakau bear striking similarities in their mode of occurrence and mineral content to those found in other tin-fields, and especially to those of Erzgebirge. The. topaz and cassiterite in the latter tin-field have been proved to be of secondary origin, and the evidence appears to be very strong for presuming that these minerals are also of secondary origin at Gunong Bakau. V.—Norr on a eigantic CepHaLopop MANDIBLE. By G. C. Crick, F.G.S., F.Z.S., of the British Museum (Natural History). [Published by permission of the Trustees of the British Museum. ] [{\HE British Museum has recently received (in the James W- Butler collection, presented by his daughter, Miss Daisy Butler) a particularly fine mandible of a gigantic fossil Cephalopod.® Unfortunately the locality of the fossil is not recorded, but as the collection contained quite a number of specimens from Bradford Abbas (Dorset) and the immediate neighbourhood, and the matrix of this specimen agrees very closely with that of those examples, there can be little doubt that the locality of the fossil is almost 1 H. C. Fergusson & A. M. Bateman, ‘‘ Geologic Features of Tin Deposits ’’ : Heonomic Geology, vol. vii, pp. 250-1, 1912. 2 Tbid.,;'p: 241. 3 Tbid., p. 237. * After deduction of part of Al, which formed 7-86 and 7-57 per cent of these rocks. > Calculated as Fee Os. 5 British Museum (Natural History), Geol. Dept., reg. No. C. 18659. G. 0. Orick—Gigantic Cephalopod Mandible. 261 certainly Bradford Abbas, or the immediate neighbourhood, and that the specimen is of Bajocian age. The fossil (Fig. 2) is obviously the calcareous portion of the upper mandible of a giant Mauwtilus-like animal, as a comparison with that structure in the recent Nautilus pompilius shows. The mandibles of Wautilus pompilius (see accompanying figures) were described by Sir Richard Owen’ as follows :— cw a Fic. 1.—Nautilus pompilius. a, inner view of lower mandible showing the dentated margin of the caleareous upper part; 6, lateral view of the same showing the widely-expanded horny lamine of this mandible; c, lateral view of the upper mandible with its hood-like expansion ; d, inner view of the same, showing the limits of the calcareous extremity of the mandible on the inner side. The calcareous extremities of the mandibles are indicated in figures b,c, d by lighter shading and a light irregular line showing the extent of the calcareous matter. This could not well be indicated in a without interfering with the dentated margin. Natural size. (After A. H. Foord, Cat. Foss. Ceph. Brit. Mus., pt. 2, 1891, fig. 76, p. 364.) ‘hese are two in number, having a vertical motion, and resembling in form the bill of the Parrot reversed, the upper mandible being encased in the lower when closed ; they are adapted posteriorly to a muscular basis, to which they owe their motions. Thus far they resemble the mandibles of the Dibranchiate Cephalopods ; but they are not composed entirely of horny matter, nor are they uniformly of a brown or black colour, their extremities being of a dense calcareous nature, and of a blueish white colour; they are also less pointed at the end; and the oral margins of the lower mandible are notched and dentated. ‘They are proportionately larger than in the Cuttle-fish, each mandible measuring in length one inch and three lines, and in vertical breadth one inch. About half an inch from their anterior extremities the horny part separates into two lamine, the exterior of which in the upper mandible is of little extent (from three to four lines), and is dilated and flattened above so as to form a triangular surface half an inch broad at the base. In the lower mandible the proportions of the two lamine are reversed, the exterior one being produced to the full extent, so as to make it appear larger than the upper mandible, which is not really the case. ‘The calcareous extremities of both mandibles are of a hardness apparently adequate to break through the densest crustacean 1 R. Owen, Memoir on the Pearly Nautilus (Nautilus pompilius), 1832, pp. 20 et seqq. 262 8G. C. Crick—Gigantie Cephalopod Mandible. coverings, or even shells of moderate thickness. That of the upper mandible is sharp-pointed, and solid to the extent of five lines from the extremity; but in the lower one the calcareous matter is deposited on both sides of a thin layer of the black horny substance and thus a combination of tough with dense matter is obtained, which much diminishes the liability to fracture. This mandible is also more hooked than the upper one, but is more obtuse at the end; it seems from its dentated margin evidently intended to break through hard substances, whilst the sharp edges of the beak of the Cuttle-fish better adapt it for cutting and lacerating the soft bodies of fish. Indeed, in the particulars just mentioned, the mandibles of Wautilus differ from those of every other known species of recent Cephalopoda.” When found fossilised, usually only the calcareous extremities are preserved, although occasionally portions of the horny substance are found associated with them.! The present fossil is represented of the natural size in the accompanying figures, and a comparison of them with corresponding figures of the upper mandible of the recent Nautelus pompilius at once reveals the true nature of the fossil; thus, Fig. 2b corresponds to the tip of Fig. 1c, and Fig. 2c corresponds to the uppermost portion of Fig. 1d. A series of papers on the mandibles of Fossil Cephalopoda has comparatively recently been published by Dr. Alfred Till,’ but the present specimen appears to differ from all the forms belonging to Nautilus-like Cephalopods that have already been described and is therefore regarded as new. Following Dr. Till’s system of nomen- clature the specimen may be named Wautilus (Rhyncholithes butleri, n.sp.) sp., signifying that the name of the mandible is Rhyncholithes butlert and that it belonged to a Wautilus-like Cephalopod of which the species has not been determined. The present fossil consists almost exclusively of the fossilised calcareous portion of an upper mandible, but it is much larger than any other specimen in the British Museum collection. It bears some remnants of the horny substance of the mandible. In the recent Nautilus pompilius (see Fig. 1c, d) the calcareous portion of the upper mandible consists of a hood-shaped upper portion supported below. by a ‘shaft’. On the inner side the surfaces of these two portions are continuous and more or less in the same plane, but on 1 See A. H. Foord, Cat. Foss. Ceph., Brit. Mus., pt. 2, 1891, fig. 79a (p. 368) and figs. 800, c (p. 369). 2 Tritt (Alfred), ‘‘ Die Cephalopodengebisse aus dem schlesischen Neokom”’ : Jahrb. d. k.k. geol. Reichsanst., Wien, Bd. lvi, 1906, pp. 89-154, pls. iv, v, text-illust. Tin (Alfred), ‘‘ Die fossilen Cephalopodengebisse’’: Jahrb. d. k.k. geol. Reichsanst., Wien, Bd. lvii, 1907, pp. 535-682, pls. xii, xiii, text-illust. Tiuu (Alfred), ‘‘ Die fossilen Cephalopodengebisse’’: Jahrb. d. k.k. geol. Reichsanst., Wien, Bd. lviii, 1908, pp. 573-608, pls. xix (i), xx (ii), text- illust. Triu (Alfred), ‘‘ Die fossilen Cephalopodengebisse ’’: Jahrb. .d. k.k. geo!. Reichsanst., Wien, Bd. lix, 1909, pp. 407-26, pl. xiii, text-illust. Trib (Alfred), ‘‘ Uber einige neue Rhyncholithen’’: Verhandl. d. k.k. geol. Reichsanst., Wien, 1911, pp. 360-5, text-illust. G. 0. Crick—Gigantic Cephalopod Mandible. 268 the outer side the median line of the surface of the ‘hood’ makes amore or less obtuse angle with that of the surface of the ‘shaft’. The measurements of the detached calcareous portion of the upper mandible of a recent Nautilus pompilius figured by Dr. Till (1906, pL iy, figs. 1, 2, 3) are: total length, 14°5mm.; breadth, 10:1 mm. ; length of hood (measured along median line of outer side), 10°5 mm. ; length of shaft (measured along median line of outer side), 8°5 mm. ; angle between the hood and the shaft (measured along the median line of the outer side), 98°. Theangle of the apex of the hood as seen from the inner side is 82°. Fie. 2.—Nawutilus (Rhyncholithes butleri, n.sp.) sp. The type-specimen. a, outer aspect showing the obtuse ridge along the median line of the hood and at h remains of the chitinous portion of the mandible; b, lateral aspect, showing at p a series of shallow pits caused perhaps by a fringed lip, and at # remains of the chitinous portion of the mandible; c, inner view showing the median protuberance. Natural size. Most probably from the Inferior Oolite of Bradford Abbas (Dorset) or of the immediate neighbourhood. Original in British Museum (Nat. Hist.), London, Geol. Dept., No. C. 18659. é The present specimen is incomplete both at the apex and at the hinder end, so that only approximate measurements are possible. They are: extreme length, 51:7 mm.; breadth, 35:6 mm. ; length of hood (measuredalong the median line of the outer surface), 38-6 mm. ; length of shaft (measured along the median line of the outer 264 G.C. Crick—Gigantic Cephalopod Mandible. surface), 33°2mm. Viewed laterally the median line of the hood is feebly convex; that of the shaft feebly concave, especially the portion near the hood. The ‘ profile-curvature’ angle, or the angle which the median line of the ‘hood’ makes with the median line of the ‘shaft’, is 94°. The hood has a prominent obtuse median ridge, the sides of the hood forming an angle of 109° with each other. Near the anterior and inner border there is a series of longitudinally- elongated pits, closed anteriorly but open posteriorly, that may perhaps have been caused by a fringed lip such as was described by Sir Richard Owen in the recent Vautilus pompilius,! and on the posterior portion of the hood there are some coarse obscure longi- tudinal ridges. The outer surface of the shaft bears both longitudinal and transverse feeble rounded ridges, giving the surface an obscurely reticulated appearance. On each side of the shaft close to the hood there are remains of the chitinous portion (marked / in figs. 2a and 6) of the mandible. Viewed laterally the inner surface of the mandible | is feebly sigmoidal, the anterior portion being concave and the posterior part convex. The anterior two-thirds of this surface is occupied by a protuberance which is widest at its posterior part, being there about 10 or 11mm. wide, and anteriorly narrows and also becomes much less prominent. The hindermost part of the inner surface has several deep irregular depressions. The angle of the hood as seen from the inner side is 61°. As to the affinities of the fossil, it most nearly resembles the specimen which d’Orbigny? described and figured in 1825 from the Corallian rocks of the Chez promontory, near La Rochelle, France, under the name of Rhyncholithes giganteus, and which was found in the same bed as a large Nautilus, which he named JVautvlus giganteus, that attained a diameter of 18 or 19 inches and was the only Cephalopod found in the bed which yielded the mandible. According to d’Orbigny’s figures that specimen was longer and narrower than the present eamiplel: its extreme length and breadth being 54°8 mm. and 31°2mm. respectively, the angle at its apex, as seen from the inner side, being 48°; also the swelling on its inner surface extends farther backward than in the present example. We are then led to ask if any Inferior Oolite Nautilus is known sufficiently large to have owned such a mandible. Dr. Foord and the present writer ‘described ® in 1890, under the name Wautilus ornatus, a species of WVautilus from the Inferior Oolite that attained a considerable size, for the British Museum collection contains an example‘ [ No. C. 578] of the species 16 inches in diameter from a quarry near Oborne Church, near Sherborne, Dorset, and another 2 feet in diameter from the Inferior Oolite of Sherborne [_No. C. 3193}. he mandible above described might then have belonged to a large example of such a species. 1 R. Owen, op. cit., p. 22. A Soa similar series of pits is figured by Foord (Cat. Foss. Ceph. Brit. Mus., pt. 2, 1891, figs. 78d, e, f) in an upper mandible from the Lias of Lyme Regis, that Dr. Till has subsequently (Jahrb. d. k.k. geol. Reichsanst., Wien, Bd. lvii (1907), Hft. 3, p. 539) named Nautilus (Rhyncholithes punctatus) nom. nov. 2 A. d’Orbigny, Ann. Sci. nat., ca v, 1825, pp. 215-17, pl. vi, Be) Li 3 Ann. Mag. Nat. Hist., [6], vol. v, p- 273, fig. 7. * Presented by George Potter, Esq., . R.M.S. ae Arthur Holmes—Radio-actiwity. 265 VI.—Ranio-acriviry and THE Earru’s THEerMaL History. By ARTHUR HOLMES, A.R.C.S., D.1.C., B.Sce., F.G.S. PART Tit.! Radio-activity and Isostasy. 14. Isosratic CompENsATION. f¥\HE distribution of land and sea implies that the earth’s outer shell is in a condition of approximate hydrostatic equilibrium. Otherwise the equatorial regions should be girdled by a continental protrusion, or else each of the polar regions should be occupied by a continental bulge. The observed fact that the inequalities of the earth’s surface exhibit neither of these conditions proves that the general ellipticity of the lithosphere does not differ greatly from that which would be assumed by a liquid spheroid having a similar distribution of density in depth. The incapacity—thus demonstrated —of the lithosphere to endure permanent stresses leads naturally to an inquiry into the conditions that maintain continents and mountain ranges above sea-level. Investigations based on the deviations of the plumb-line from the vertical and on the varying intensity of gravity indicate beyond doubt that the elevated tracts of the globe owe their support to a deficiency of density in their deep-seated foundations, while the great sunken areas owe their depression to a corre- sponding excess of density in the underlying rocks. Thus has arisen the conception of zsostasy, a word which was coined by Dutton *in 1889 to express the state of hydrostatic* balance that maintains in position elevated and depressed columns of the lithosphere. Columns of equal cross-sectional area, though of different heights, may have the same mass on account of their respective densities, and if so, at a certain level beneath the mean surface of the geoid, each one will exert the same pressure on the zone below. The regional perfection of isostasy, and its local limitations, have been. demonstrated by the geodetic observations of nearly seventy years. Petit,°in 1849, found that the Pyrenees deflected the vertical much less than was to be expected. Archdeacon Pratt,®.in 1852, discovered a similar anomaly in the case of the Himalayas; and during the later months of the same year Airy,’ then Astronomer Royal, propounded a theory of compensation explaining the anomalies in terms of underlying density. Putnam and Gilbert® established a considerable degree of isostatic equilibrium for the United States in 1895, and their conclusions have been verified in still greater detail ? Parts I and II appeared in the GEoL. MaG. for February and March, 1915, pp. 60-71, 102-12. = Tat. Jeffreys, “ The Mechanical Properties of the Earth’? : The Observatory, 491, p. 348, 1915. 3 Bull. Phil. Soc. Wash., xi, p. 53, 1889. * Or hydrodynamic ? ? ° C.R,, vol. xxix, p. 730, 1849. 6 Phil. Trans. Roy. Soc., vol. exlv, 1885. ” Thid. 8 Bull. Phil. Soc. Wash., xiii, p. 31, 1895. 266 Arthur Holmes—Radio-activity. by the laborious studies of Hayford and Bowie.’ In India,? along the margins of the continents* and over the ocean basins,‘ a similar but less intimate association between terrestrial relief and underlying density has been recognized. At least for the broader features of the earth’s topography the theory of isostasy may therefore be Tee as established.° 15. Lrrirs or Isosraric EQuinisRium. Hayford and Bowie, in their analysis of the results of the U.S. Geodetic Survey, found that by introducing the conception of isostatic compensation they were able to reduce deflection anomalies and gravity anomalies to respectively one-tenth and one-quarter of the value these anomalies would have had without applying the compensation hypothesis. The depth of compensation which most successfully reduces the anomalies is 122 km., though it should be noticed that the depth chosen may range from 66 to 305 km. and yet give an almost equally good reduction. Hayford suggests that ‘‘ the maximum horizontal extent which a topographic feature may have and still escape compensation is between one square mile and one square degree ”’ (op. cit., 1906, p. 169). This conclusion implies that the earth’s crust is so weak that the weight of accumulating sediments on the sea floor may well cause the latter to sink. Barrell, however, has made a careful study of the Nile and Niger deltas, and deduces from their thickness and great areal extent a much stronger crust than is possible on Hayford’s view of local compensation. Moreover, he demonstrates that the geodetic results of the United States, ‘‘instead of indicating local compensation to limits of less than one square degree, show on the contrary a ready capacity of the crust under the United States to carry over areas of from 5 to 10 or 15 square degrees, and exceptionally over even larger areas, departures from equilibrium greater than the mean” (op. cit., 1914, p. 165). Barrell supports his view of a strong crust by citing the immense departures from isostatic equilibrium exhibited by areas in India, Japan, and Norway, by the great basaltic dome of Mauna Kea, and by the Tonga Plateau and Deep. That the strength so manifested is greater than that of the surface rocks is only to be expected, for the experiments of Adams have proved beyond question that granite, for example, becomes increasingly stronger with increase of pressure.° There can be no doubt that North America is at present in a state of much 1 Hayford, Proc. Wash. Acad. Sci., vol. viii, p. 25, 1906; U.S. Coast and Geodetic Survey, 1909 and 1910; Science, vol. xxxiii, p. 199, 1911. Hayford and Bowie, U.S. Coast and Geodetic Survey, 1912, Spec. Pub. 10. Bowie, U.S. Coast and Geodetic Survey, 1912, Spec. Pub. 12; Am. Jowrn. Sev., vol. xxxiii, p. 237, 1912. 2 Burrard, Survey of India, 1912, Prof. Paper 12; Crosthwants Survey of India, 1912, Prof. Pap. 13. 3 Schidtz, Skrift. Vedensk. Selsk. Christiania, 1908, No. 6. + Hecker, Veréff. k. Preuss. geodat. Inst. Berlin, 1903, No. 11; 1908, No. 12. See also Bauer, Am. Journ. Sci.; vol. xxxi, p. 1,1911; vol. xxxiii, p. 245, 1912. ° Gilbert, U.S.G.S., 1913, Prof. Pap. 85-C. Barrell, Jowrn. Geol., vol. xxii, Nos. 1-8, 1914; vol. xxiii, Nos. 1, 5, and6, 1915. § Journ. Geol., vol. xx, p. 97, 1912. re a Se ee eee at Arthur Holmes—Radio-activity. 267 more perfect isostatic equilibrium than are most areas of the earth’s surface, and the evidence it affords of the strength of the earth’s crust is therefore insufficient and inconclusive. Barrell justly concludes that ‘‘Isostasy . . . is nearly perfect, or is very imperfect, or even non-existent, according to the size and relief of the area considered ”’. For the continents and oceans the degree of adjustment is high ; within areas of 250 km. in diameter the departure from equilibrium may be high; while individual peaks and even small ranges may be wholly supported by the rigidity of the underlying rocks. 16. THe AstHENOSPHERE. Barrell has shown that the greater departures from isostasy impose very considerable stress differences on the zone of compensation, and he has applied this fact to a deduction of the strength of the litho- sphere at various depths. If a series of wave-like curves represent the profile of uncompensated hills and valleys, or of oceanic islands and troughs, then the maximum stress difference is imposed at a depth of 1/27 of the wave length. In various parts of the world such wave lengths can be approximately measured. For example, in the ridges and troughs of the Pacific the wave lengths are from 300 to 500 km. Even if the strains set up by these loads were entirely unmitigated by compensation, the maximum stresses would not be applied at depths greater than 80 km. That is to say, the existing inequalities which lack complete compensation are responsible for loads that are almost wholly borne by the zone of compensation as defined by Hayford. Greater inequalities of topography would, if uncompensated, throw stress differences to correspondingly greater depths, and the -fact that such inequalities do not exist unless they are largely or wholly compensated implies that the rocks below the zone of ‘compensation are too weak to support them. Otherwise, if the rocks were rigid enough to support great mountain ranges, why should _the latter be compensated at all? It is a natural conclusion that the lithosphere (limited at its base by the bottom of the zone of compensation) is strong, especially in its upper half, compared with the underlying zone. For the latter Barrell proposes the name asthenosphere—sphere of weakness. The evidence he brings forward leads him to suggest the following approximate figures, to illustrate the variation of strength with depth (op. cit., 1915, p. 44) :— Depth in Strength in kilometres. percentage. 0 100+ 20 400 Lithosphere é 5 ae 50 25 100 ele 200 8 Asthenosphere 300 5 400 4 The relative weakness and plasticity of the asthenosphere is capable of a second proof based on the implications of isostasy. Denudation 1 At the surface strong limestone or granite can sustain a stress difference of 25,000 pounds per square inch (1,750 kg. per sq. cm.). 268 Arthur Holmes—Radio-activity. involves a paring away of the upper surface of the lands, and an accumulation of the resulting debris around their borders. The land columns become lighter; the sea floor is weighed down. An equally certain fact, attested by many an eloquent chapter of geological history, is that during the transfer of load from continent to ocean floor the former rises and the latter sinks. What is the hidden mechanism that restores the isostatic balance? Corresponding to the lateral movement of sediment there must be a lateral counter- movement in the rocks far below. At first Hayford considered that this undertow took place within the zone of compensation, but Barrell’ has convincingly shown that this view is untenable, and Hayford? in his latest pronouncement has apparently abandonedit. ‘he undertow must be below the zone of compensation, and consequently the matter at greater depths must be somewhat plastic. Moreover, to maintain an isostatic balance between segments of the lithosphere so extensive as continents and ocean basins the plastic zone—the asthenosphere— must be very thick, certainly several hundreds of kilometres. Quite independent evidence comes from another branch of geophysics. Tt has sometimes been assumed that a viscous magmatic zone might exist within the earth between a rigid crust and a rigid core. Schweydar * has tested this theory by analysing the results of earth- tide measurements made with the horizontal pendulum. He proved conclusively that a magmatic zone of the kind imagined could not exist, and showed that the results pointed—as one alternative—to the existence of a slightly plastic zone extending downwards from a depth of 120 km. and fading out some 600 km. below. The existence of the asthenosphere is thus supported by arguments based on three different lines of investigation. In the remaining part of this paper its existence will be accepted, and used asa criterion by which to test the distribution of temperature within the earth that was deduced in Part II. 17. Tue Temperature Curve TESTED BY Isosrasy. The temperature at any depth below the earth’s surface has been regarded as the sum of three components—(1) that due to the initial temperature at or near the surface, and since modified by cooling ; (2) that implied by the variation of the fusion-point with depth, as controlled by pressure; and (3) that due to the local distribution of the radio-active elements. — | These three components are mathematically expressed for an depth 2 in equations 9 and 18 on p. 111 of Part II (March, 1919). In calculating the list of temperatures there tabulated, it was. assumed that the downward increase of temperature due to pressure was 0:00005° C. per cm., or 5° C. per km. Such an assumption cannot, of course, be applied satisfactorily to any considerable depth. We do not know to what extent the law connecting pressure with a rise of the fusion-point of a mineral is linear, and moreover the distribution of minerals in depth cannot be a simple continuation of 1 Barrell, op. cit., p. 677, 1914. 2 Hayford, Proc. Am. Phil. Soc., vol. liv, p. 298, 1915. 3 Verdff. Preuss. geodat. Inst., No. 54, 1912. Arthur Holmes—Radio-activity. 269 what is observed at the surface. If, therefore, the pressure component could be left out of the discussion altogether, and a disturbing factor thus avoided, a considerable advantage would be gained. Now, for the present purpose, this can readily be done, for it is required to compare the fusion-points of certain minerals and rocks! with the temperatures at depths appropriate to their occurrence within the earth. Let us suppose that for a given mineral or rock the rise of the fusion-point at a depth 2 is mx. Then the pressure component of temperature at that depth willalso be mz. The fusion- point may be expressed as S + mx where S is the fusion-point at the surface, and the temperature as 7’+ mx where 7'is the temperature due to other factors than the pressure component. Consequently, in plotting fusion-point and temperature curves the differential relation of one to the other will not be affected by plotting S and 7’respectively instead of S + mx and 7+ mz. Thus, at every depth, «, the appropriate but at present unknown value of mz, may be omitted without detriment, and with the advantage that a doubtful extra- polation is completely avoided. 1800;C Pa Sy SEES NWS EE PG EE I Si barn ip MR nL MCS ON CM Ree eG LE {600 : Enstatite Olivine Diopside 1200} abradorite r 800° F ~ x " ‘\ 400°